Bromine, Chemical Element - reaction, water, uses, elements, metal, gas, number, name PRONUNCIATION BRO-meen Nearly 90 percent of all bromine produced comes from the United States, Israel, or the United Kingdom. In 1996, about 450,000,000 kilograms (one billion pounds) of the element were produced worldwide. The largest single use of the element is in the manufacture of flame retardants. Flame retardants are chemicals added to materials to prevent burning or to keep them from burning out of control. Other major uses are in the manufacture of drilling fluids, pesticides, chemicals for the purification of water, photographic chemicals, and as an additive to rubber. Discovery and naming Compounds of bromine had been known for hundreds of years before the element was discovered. One of the most famous of these compounds was Tyrian purple, also called royal purple. (Tyrian comes from the word Tyre, an ancient Phoenician city.) Only very rich people or royalty could afford to buy fabric dyed with Tyrian purple.

It was obtained from a mollusk (shell fish) found on the shores of the Mediterranean Sea (a large body of water bordered by Europe, Asia, and Africa). In 1825, Löwig enrolled at the University of Heidelberg in Germany to study chemistry. He continued an experiment he had begun at home in which he added chlorine to spring water. The addition of ether to that mixture produced a beautiful red color. Löwig suspected he had discovered a new kind substance. A professor encouraged him by suggesting he study the substance in more detail. As these studies progressed, Balard published a report in a chemical journal that announced the discovery of the new element bromine. The element had all the properties of Löwig's new substance. The two chemists had made the discovery at nearly the same time! Balard, however, is credited as the discoverer of bromine, because scientists acknowledge the first person to publish his or her findings. In Greek, the word bromos means "stench" (strong, offensive odor). Bromine lives up to the description. The odor is intense and highly irritating to the eyes and lungs. Chemists found that bromine belonged in the halogen family.

They knew that it had properties similar to other halogens and placed it below fluorine and chlorine in the periodic table. Physical properties Only two liquid elements exist—bromine and mercury. At room temperature, bromine is a deep reddish-brown liquid. It evaporates easily, giving off strong fumes that irritate the throat and lungs. Bromine boils at 58.8°C (137.8°F), and its density is 3.1023 grams per cubic centimeter. Bromine freezes at -7.3°C (18.9°F). A laboratory vessel holds the solid, liquid, and gas states of bromine. Bromine dissolves well in organic liquids—such as ether, alcohol, and carbon tetrachloride—but only slightly in water. Organic compounds contain the element carbon. Chemical properties Bromine is a very reactive element. While it is less reactive than fluorine or chlorine, it is more reactive than iodine. It reacts with many metals, sometimes very vigorously. For instance, with potassium, it reacts explosively. Bromine even combines with relatively unreactive metals, such as platinum and palladium.

Occurrence in nature Bromine is too reactive to exist as a free element in nature. Instead, it occurs in compounds, the most common of which are sodium bromide (NaBr) and potassium bromide (KBr). These compounds are found in seawater and underground salt beds. These salt beds were formed in regions where oceans once covered the land. When the oceans evaporated (dried up), salts were left behind—primarily sodium chloride (NaCl), potassium chloride (KCl), and sodium and potassium bromide. Later, movements of the Earth's crust buried the salt deposits. Now they are buried miles underground. The salts are brought to the surface in much the same way that coal is mined. Bromine is a moderately abundant element. Its abundance in the Earth's crust is estimated to be about 1.6 to 2.4 parts per million. It is far more abundant in seawater where it is estimated at about 65 parts per million. In some regions, the abundance of bromine is even higher. For example, the Dead Sea (which borders Israel and Jordan), has a high level of dissolved salts. The abundance of bromine there is estimated to be 4,000 parts per million.

The salinity, or salt content, is so high that nothing lives in the water. This is why it is called the Dead Sea. Isotopes Two naturally existing isotopes of bromine exist, bromine-79 and bromine-81. Isotopes are two or more forms of an element. Isotopes differ from each other according to their mass number. The number written to the right of the element's name is the mass number. The mass number represents the number of protons plus neutrons in the nucleus of an atom of the element. The number of protons determines the element, but the number of neutrons in the atom of any one element can vary. Each variation is an isotope. At least 16 radioactive isotopes of bromine are known also. A radioactive isotope is one that breaks apart and gives off some form of radiation. Radioactive isotopes are produced when very small particles are fired at atoms. These particles stick in the atoms and make them radioactive. No isotope of bromine has any important commercial use. The salinity, or salt content, is so high that nothing lives in the water. This is why it is called the Dead Sea.

Extraction The method used by Lowig and Balard to collect bromine continues to be used today. Chlorine is added to seawater containing sodium bromide or potassium bromide. Chlorine is more active than bromine and replaces bromine in the reaction: Uses The most important use of bromine today is in making flame retardant materials. Many materials used in making clothing, carpets, curtains, and drapes are flammable, and if a flame touches them, they burn very quickly. Chemists have learned how to make materials more resistant to fires by soaking them in a bromine compound. The compound coats the fibers of the material. The bromine compound can also be chemically incorporated into the material. The bromine compounds used in flame retardants are often complicated. One such compound is called tris(dibromopropyl)phosphate ((Br 2 C 3 H 5 O) 3 PO). However, this compound has been found to be a carcinogen (cancer-causing substance). Its use, therefore, has been severely restricted. About 20 percent of all bromine is used in drilling wells.

Calcium bromide (CaBr 2 ), sodium bromide (NaBr), or zinc bromide (ZnBr 2 ) are added to the well to increase the efficiency of the drilling process. Bromine is also important in the manufacture of pesticides, chemicals used to kill pests. Methyl bromide (CH 3 Br) has been used for years to treat crop lands. Methyl bromide is sprayed on the surface or injected directly into the ground. Some methyl bromide always evaporates into the air where it damages the ozone layer. Ozone (O 3 ) gas filters out a portion of the ultraviolet (UV) radiation from the sun. UV radiation causes skin cancer, sunburn, and damage to plants and fragile organisms. Worldwide production of methyl bromide will end in 2001 because of its effect on the ozone layer. The United States plans to stop production of the compound even earlier. Farmers believe nothing works as well as methyl bromide in eliminating certain pests. They are concerned that crop production will suffer if methyl bromide is banned. The most important use of bromine today is in making flame retardant materials.

Ethylene dibromide (C 2 H 4 Br 2 ) is a bromide compound added to leaded gasoline. The lead in "leaded gasoline" is tetraethyl lead (Pb(C 2 H 5 )) 4 ). It helps fuels burn more cleanly and keeps car engines from "knocking." "Knocking" is a repetitive metallic banging sound that occurs when there are ignition problems Bromine compounds increase the efficiency of the drilling process in oil rigs. with a car's engine. "Knocking" reduces the efficiency of a car engine. But leaded gasoline gives off free lead as it burns. Free lead is a very toxic element that causes damage to the nervous system. Ethylene dibromide is added to react with free lead and convert it to a safe compound. Ethylene dibromide does not completely solve the problem. Some free lead still escapes into the atmosphere. Leaded gasoline has been banned in the United States for many years but is still used in other countries. The most popular element for purifying public water supplies and swimming pools used to be chlorine. Bromine compounds have become more popular for their superior bacteria killing power. Health effects Bromine is toxic if inhaled or swallowed.

It can damage the respiratory system and the digestive system, and can even cause death. It can also cause damage if spilled on the skin. Also read article about Bromine from Wikipedia User Contributions: What are the Halogens in the Periodic Table? - Quora Quora Daniel James Berger , PhD in organic chemistry The elements in Group 17 of the periodic table ( The Old fashioned name for Group 17 is Group VII ) are known collectively as The Halogens. They are the elements Fluorine, ( atomic number 9 ), Chlorine, ( atomic number 17 ), Bromine ( atomic number 35 ), Iodine ( atomic number 53 ), Astatine ( atomic number 85 ), and a newly discovered element not yet given a name, that has an atomic number of 117, ( Discovered in 2010). However both Astatine and Element No. 117 are too radioactive to be made in quantities that can be weighed. They are man made elements that have very short half lives; so decay into other elements before one has the chance to make any of their compounds.

So in most laboratories Halogen chemistry is essentially about the study of Fluorine, Chlorine, Bromine & Iodine. The word Halogen was coined in 1842 by the Swedish Chemist Berzelius ( 1779 - 1848 ). It is a made up Swedish word which literally means "Salt producer" in Swedish. A name in keeping with the reactive nature of these elements. Lots of Halogen salts are known. Eg. Sodium chloride. Potassium fluoride. Sodium Bromide. These elements are all members of the same group, because all of their atoms have the same number of electrons in their outermost shell or orbit. Group 17 elements all have 7 electrons in their outermost orbit. ​ ​The Periodic Table highlighting Group 17. Fluorine As mentioned previously fluorine has an atomic number of 9. This means that an atom of fluorine will have in addition to 9 protons in the nucleus of its atom, it will have a total of 9 electrons orbiting its nucleus. An individual proton always has a charge of +1 and an individual electron always has a charge of -1.

We have 9 protons in an atom of fluorine each having a charge of +1, plus 9 electrons in that same atom orbiting the nucleus of that atom. ( +1 X 9 ) + (-1 X 9 ) = 0. So the atom is electrically neutral. This is true for all neutral atoms of fluorine. The 9 electrons are arranged in 2 shells or orbit. 2 of the 9 electrons orbit in the 1st shell or orbit. The remaining 7 electrons orbit in a larger shell. The 7 electrons in the outermost orbit of all Halogens are the electrons that participate in chemical reactions. During chemical reactions the number of electrons in the outermost orbit can go up or down. Up to a max of 8, and down to 0 ( in theory ). Compare with Na+1 or with Li+1 ​ Written Feb 7, 2016 The halogens are the family of chemical elements that includes fluorine (atomic symbol F), chlorine (Cl), bromine (Br), iodine (I), and astatine (At). The halogens make up Group VIIA of the Periodic Table of the elements. Elemental halogens are diatomic molecules.

However, due to their high reactivity, the halogens are never found in nature in native form. The family name means "salt-forming," from the Greek for salt, "hals", and for generating "genes". The salinity of the oceans on Earth is due in large part to such halogen salts (halides) as sodium chloride (NaCl) and potassium iodide (KI). Halogens display physical and chemical properties typical of nonmetals. They have relatively low melting and boiling points that increase steadily down the group. Near room temperature, the halogens span all of the physical states: Fluorine and chlorine are gases, bromine is a liquid, and iodine is a solid. All of the elements are colored, with the color becoming more intense moving down the group. Fluorine gas is pale yellow, and chlorine gas is a yellowish green. Liquid bromine and its vapors are brownish red. Solid iodine appears as shiny, dark gray crystals, and the vapors are a deep purple. The halogens are poor thermal and electrical conductors in all phases, and as solids they are brittle and crumbly.

The halogens have distinctive, unpleasant odors, will burn exposed flesh, and are toxic. The neutral atoms of the halogens possess seven outer electrons. An additional electron can be added to halogen atoms to form singly charged negative ions. These ions have a closed outer-shell configuration. Electronegativity is a measure of the ability of an atom of one element to remove an electron from an atom of another element. As a group, the halogens are among the most electronegative elements. Fluorine has the highest electronegativity of all the elements. Halogens are so reactive that all the elements except helium and neon have been found to react with at least one of the halogens. Fluorine is always assigned a formal oxidation number of –1, whereas the other halogens can exhibit a range of oxidation numbers 526 Views · View Upvotes · Answer requested by What group does Fluorine belong to? | Reference.com What group does Fluorine belong to? A: Quick Answer Fluorine belongs to group number 17, which is the halogen family of elements that also includes astatine, iodine, bromine and chlorine.

The element fluorine is a highly reactive gas at room temperature that is not found freely in nature. Fluorine has a melting point of 363.32 degrees F, a boiling point of 306.62 degrees F and a density of 0.001696 grams per cubic centimeter. Reactions of Main Group Elements with Halogens - Chemistry LibreTexts Reactions of Main Group Elements with Halogens Last updated Answers This section describes the chemistry of halogens with the main group elements such as the alkali metals , alkaline earth metals , and Groups 13 and 14 . The word halogen itself means "salt former" in Greek. Halogens such as chlorine, bromine and iodine have properties that enable them to react with other elements to form important salts such as sodium chloride, also known as table salt. Properties of Halogens Elements such as fluorine, chlorine, bromine, iodine, and astatine belong to Group 17, the halogen group. At room temperature fluorine is a yellow gas, chlorine is a pale green gas, bromine is a red liquid, and iodine is a purple solid.

Astatine is a radioactive element, and exists in nature only in small amounts. All the halogens exist as diatomic molecules. They have high ionization energies and form the most electronegative group of elements. Their electron configuration, ns2np5, allows them to easily react with Group 1 and 2 metals; each halogen tends to pick up one electron, and the Group 1 and Group 2 elements each tend to lose one or two electrons, respectively. Halogens therefore react most vigorously with Group 1 and Group 2 metals of all main group elements. Reaction with Water From a standard reduction potential table, it is determined that iodine and bromine cannot oxidize water to oxygen because they have smaller reduction potentials than oxygen. Thus, iodine and bromine do not react with water. However, fluorine and chlorine have larger reduction potentials, and can oxidize water.

Fluorine reacts with water vapor to form oxygen and ozone: \[2F_2(g) + 2H_2O(g) \rightarrow 4HF(g)+ O_2(g) \] \[3F_2(g) + 2H_2O(g) \rightarrow 6HF(g) + O_3(g)\] The reaction of water with chlorine, shown below, proceeds very slowly. \[Cl_2 + H_2O \rightarrow H^+ + Cl^- + HClO\] Chlorine and bromine are moderately soluble in water. These solutions form solid hydrates within an ice lattice. These solutions are good oxidizing agents. Chlorine reacts reversibly with water to produce acids as in the following example, in which chloric acid and hydrochloric acid are formed: \[Cl_2 + H_2O \rightleftharpoons HClO + HCl\] Iodine is slightly soluble in water. It has the lowest standard reduction potential of the halogens, and is therefore the least powerful oxidizing agent. Air and other reagents can oxidize acidified solution of iodide ions.

Reaction with Hydrogen All the halogens react directly with hydrogen, forming covalent bonds and—at sufficient levels of purity—colorless gases at room temperature. Hydrogen reacts with fluorine, chlorine, bromine, and iodine, forming HF, HCl, HBr, and HI, respectively. The bond strength of these molecules decreases down the group: \(HF > HCl > HBr > HI\). Iodine and hydrogen react non-spontaneously to produce hydrogen iodide: \[H_2 + I_2 \rightarrow 2HI\] All the hydrogen halides are soluble in water, in which they form strong acids (with the exception of \(HF\)). The general equation of hydrogen halide for the acid reaction is given below: \[HX + H_2O \rightarrow H_3O^+ + X^-\] Group 1: The Alkali Metals All the alkali metals react vigorously with halogens to produce salts, the most industrially important of which are NaCl and KCl.

\[ 2Na(s) + Cl_2(g) \rightarrow 2NaCl(s)\] Sodium Chloride is used as a preservative for meat and to melt the ice on the roads (via freezing point depression ). KCl is important for plant fertilizers because of the positive impact of potassium on plant growth. These metal halides form white ionic crystalline solids and are all soluble in water except LiF, because of its high lattice enthalpy attributed to strong electrostatic attraction between Li+ and F- ions. Group 2: The Alkaline Earth Metals The alkaline earth metals react to form hydrated halides. These halides are ionic except for those involving beryllium (the least metallic of the group).

Because alkaline earth metals tend to lose electrons and halogen atoms tend to gain electrons ( Table P2 ), the chemical reaction between these groups is the following: \[M + X_2 \rightarrow MX_2\] Atomic and physical properties of Periodic Table Group 7 (the halogens) ATOMIC AND PHYSICAL PROPERTIES OF THE GROUP 7 ELEMENTS (THE HALOGENS) This page explores the trends in some atomic and physical properties of the Group 7 elements (the halogens) - fluorine, chlorine, bromine and iodine. You will find separate sections below covering the trends in atomic radius, electronegativity, electron affinity, melting and boiling points, and solubility. There is also a section on the bond enthalpies (strengths) of halogen-halogen bonds (for example, Cl-Cl) and of hydrogen-halogen bonds (e.g. H-Cl) Even if you aren't currently interested in all these things, it would probably pay you to read the whole page. The same ideas tend to recur throughout the atomic properties, and you may find that earlier explanations help to you understand later ones.

Trends in Atomic Radius Note: You will find atomic radius covered in detail in another part of this site. If you choose to follow this link, use the BACK button on your browser to return quickly to this page. You can see that the atomic radius increases as you go down the Group. Explaining the increase in atomic radius The radius of an atom is governed by the number of layers of electrons around the nucleus the pull the outer electrons feel from the nucleus. Compare fluorine and chlorine: Cl 2,8,7 In each case, the outer electrons feel a net pull of 7+ from the nucleus. The positive charge on the nucleus is cut down by the negativeness of the inner electrons. This is equally true for all the other atoms in Group 7. The outer electrons always feel a net pull of 7+ from the centre. The only factor which is going to affect the size of the atom is therefore the number of layers of inner electrons which have to be fitted in around the atom. Obviously, the more layers of electrons you have, the more space they will take up - electrons repel each other. That means that the atoms are bound to get bigger as you go down the Group.

Trends in Electronegativity Electronegativity is a measure of the tendency of an atom to attract a bonding pair of electrons. It is usually measured on the Pauling scale, on which the most electronegative element (fluorine) is given an electronegativity of 4.0. Note: You will find electronegativity covered in detail in another part of this site. If you choose to follow this link, use the BACK button on your browser to return quickly to this page. Notice that electronegativity falls as you go down the Group. The atoms become less good at attracting bonding pairs of electrons. Explaining the decrease in electronegativity This is easily shown using simple dots-and-crosses diagrams for hydrogen fluoride and hydrogen chloride. The bonding pair of electrons between the hydrogen and the halogen feels the same net pull of 7+ from both the fluorine and the chlorine. (This is exactly the same sort of argument as you have seen in the atomic radius section above.) However, in the chlorine case, the nucleus is further away from that bonding pair. That means that it won't be as strongly attracted as in the fluorine case.

The larger pull from the closer fluorine nucleus is why fluorine is more electronegative than chlorine is. Summarising the trend down the Group As the halogen atoms get bigger, any bonding pair gets further and further away from the halogen nucleus, and so is less strongly attracted towards it. In other words, as you go down the Group, the elements become less electronegative. Trends in First Electron Affinity Defining first electron affinity The first electron affinity is the energy released when 1 mole of gaseous atoms each acquire an electron to form 1 mole of gaseous 1- ions. This is more easily seen in symbol terms. It is the energy released (per mole of X) when this change happens. First electron affinities have negative values. For example, the first electron affinity of chlorine is -349 kJ mol-1. By convention, the negative sign shows a release of energy. The first electron affinities of the Group 7 elements Note: You will find electron affinity covered in detail in another part of this site. The current page duplicates much of that material, but you might like to read it again in different words.

If you choose to follow this link, use the BACK button on your browser to return quickly to this page. Notice that the trend down the Group isn't tidy. The tendency is for the electron affinities to decrease (in the sense that less heat is given out), but the fluorine value is out of line. The electron affinity is a measure of the attraction between the incoming electron and the nucleus. The higher the attraction, the higher the electron affinity. In the bigger atom, the attraction from the more positive nucleus is offset by the additional screening electrons, so each incoming electron feels the effect of a net 7+ charges from the centre - exactly as when you are thinking about atomic radius or electronegativity. As the atom gets bigger, the incoming electron is further from the nucleus and so feels less attraction. The electron affinity therefore falls as you go down the Group. But what about fluorine? That is a very small atom, with the incoming electron quite close to the nucleus. Why isn't its electron affinity bigger than chlorine's? There is another effect operating. When the new electron comes into the atom, it is entering a region of space already very negatively charged because of the existing electrons.

There is bound to be some repulsion, offsetting some of the attraction from the nucleus. In the case of fluorine, because the atom is very small, the existing electron density is very high. That means that the extra repulsion is particularly great and lessens the attraction from the nucleus enough to lower the electron affinity below that of chlorine. Trends in Melting Point and Boiling Point You will see that both melting points and boiling points rise as you go down the Group. If you explore the graphs, you will find that fluorine and chlorine are gases at room temperature, bromine is a liquid and iodine a solid. Nothing very surprising there! Explaining the trends in melting point and boiling point All of the halogens exist as diatomic molecules - F2, Cl2, and so on. The intermolecular attractions between one molecule and its neighbours are van der Waals dispersion forces. Note: If you aren't sure about van der Waals dispersion forces , you will find them covered in detail in another part of this site. You won't understand the next bit unless you are happy about dispersion forces and how they vary with the size of the molecule. Use the BACK button on your browser to return quickly to this page.

As the molecules get bigger there are obviously more electrons which can move around and set up the temporary dipoles which create these attractions. The stronger intermolecular attractions as the molecules get bigger means that you have to supply more heat energy to turn them into either a liquid or a gas - and so their melting and boiling points rise. Solubilities Solubility in water Fluorine reacts violently with water to give hydrogen fluoride gas (or a solution of hydrofluoric acid) and a mixture of oxygen and ozone. So thinking about its solubility is pointless. Chlorine, bromine and iodine all dissolve in water to some extent, but there is no pattern in this. The following table shows the solubility of the three elements in water at 25°C. chlorine 0.091 bromine0.21 iodine0.0013 Note: These figures come from page 476 of Advanced Inorganic Chemistry (third edition) by Cotton and Wilkinson. Chlorine solution in water is pale green. Bromine solution in water is anything from yellow to dark orange-red depending on how concentrated it is. Iodine solution in water is very pale brown.

Chlorine reacts with water to some extent to give a mixture of hydrochloric acid and chloric(I) acid - also known as hypochlorous acid. The reaction is reversible, and at any one time only about a third of the chlorine molecules have actually reacted. You will sometimes find the chloric(I) acid written as HOCl. That represents the way the atoms are actually joined together. Bromine and iodine do something similar, but to a much lesser extent. In both cases, about 99.5% of the halogen remains as unreacted molecules. The solubility of iodine in potassium iodide solution Although iodine is only faintly soluble in water, it does dissolve freely in potassium iodide solution to give a dark red-brown solution. There is a reversible reaction between iodine molecules and iodide ions to give I3- ions. These are responsible for the colour. In the lab, iodine is often produced by oxidation of a solution containing iodide ions, so this colour is actually quite familiar. As long as there are any excess iodide ions present, the iodine will react with them to make the I3- ions.

Once the iodide ions have all reacted, the iodine is precipitated as a dark grey solid, because there isn't anything left for it to react with to keep it in solution. Solubility in hexane The halogens are much more soluble in organic solvents like hexane than they are in water. Both hexane and the halogens are non-polar molecules attracted to each other by van der Waals dispersion forces. That means that the attractions broken (between hexane molecules and between halogen molecules) are similar to the new attractions made when the two substances mix. The colours of the solutions formed are much what you would expect. Solutions of iodine in organic solvents tend to be pinky-purple colour. Bond enthalpies (bond energies or bond strengths) Bond enthalpy is the heat needed to break one mole of a covalent bond to produce individual atoms, starting from the original substance in the gas state, and ending with gaseous atoms. So for chlorine, Cl2(g), it is the heat energy needed to carry out this change per mole of bond: For bromine, the reaction is still from gaseous bromine molecules to separate gaseous atoms.

Bond enthalpy in the halogens, X2(g) A covalent bond works because the bonding pair is attracted to both the nuclei at either side of it. It is that attraction which holds the molecule together. The size of the attraction will depend, amongst other things, on the distance from the bonding pair to the two nuclei. As with all halogens, the bonding pair will feel a net pull of 7+ from both ends of the bond - the charge on the nucleus offset by the inner electrons. That will still be the same whatever the size of the halogen atoms. As the atoms get bigger, the bonding pair gets further from the nuclei and so you would expect the strength of the bond to fall. So . . . are the actual bond enthalpies in line with this prediction? The bond enthalpies of the Cl-Cl, Br-Br and I-I bonds fall just as you would expect, but the F-F bond is way out of line! Because fluorine atoms are so small, you might expect a very strong bond - in fact, it is remarkably weak. There must be another factor at work as well.

As well as the bonding pair of electrons between the two atoms, each atom has 3 non-bonding pairs of electrons in the outer level - lone pairs. Where the bond gets very short (as in F-F), the lone pairs on the two atoms get close enough together to set up a significant amount of repulsion. In the case of fluorine, this repulsion is great enough to counteract quite a lot of the attraction between the bonding pair and the two nuclei. This obviously weakens the bond. Bond enthalpies in the hydrogen halides, HX(g) Where the halogen atom is attached to a hydrogen atom, this effect doesn't happen. There are no lone pairs on a hydrogen atom! As the halogen atom gets bigger, the bonding pair gets more and more distant from the nucleus. The attraction is less, and the bond gets weaker - exactly what is shown by the data. There is nothing complicated happening in this case. This is important in the thermal stability of the hydrogen halides - how easily they are broken up into hydrogen and the halogen on heating. Hydrogen fluoride and hydrogen chloride are very stable to heat. They don't split up into hydrogen and fluorine or chlorine again if heated to any normal lab temperature.

Hydrogen bromide splits slightly into hydrogen and bromine on heating, and hydrogen iodide splits to an even greater extent. As the bonds get weaker, they are more easily broken. Note: Breaking the hydrogen-halogen bond is only one of the steps in the overall reaction, of course. You don't end up with hydrogen atoms and halogen atoms - you get diatomic molecules, H2 and X2. If you have done some energetics calculations, it would be a useful exercise to use bond enthalpies and atomisation enthalpies to calculate the overall enthalpy changes for the decomposition of the hydrogen halides. (Remember that bond enthalpies only apply to substances in the gas state, and bromine and iodine would end up as liquid and solid respectively. Using atomisation enthalpies for the halogens avoids this problem. If you don't understand what I am talking about, you don't yet have enough knowledge to be able to do this.) Questions to test your understanding If this is the first set of questions you have done, please read the introductory page before you start. You will need to use the BACK BUTTON on your browser to come back here afterwards.

Properties of the Halogens About Watch and Favorite Watch Watching this resources will notify you when proposed changes or new versions are created so you can keep track of improvements that have been made. Favorite Favoriting this resource allows you to save it in the “My Resources” tab of your account. There, you can easily access this resource later when you’re ready to customize it or assign it to your students. Properties of the Halogens Halogens (fluorine, chlorine, bromine, iodine, astatine) are nonmetal elements that are highly electronegative and reactive. Learning Objective Describe the physical and chemical properties of halogens. Key Points Halogens are nonmetals in group 17 (or VII) of the periodic table. Down the group, atom size increases. As a diatomic molecule , fluorine has the weakest bond due to repulsion between electrons of the small atoms. Due to increased strength of Van der Waals forces down the group, the boiling points of halogens increase. Therefore, the physical state of the elements down the group changes from gaseous fluorine to solid iodine. Due to their high effective nuclear charge , halogens are highly electronegative .

Therefore, they are highly reactive and can gain an electron through reaction with other elements. Halogens can be harmful or lethal to biological organisms in sufficient quantities. Terms Register for FREE to remove ads and unlock more features! Learn more Full Text The halogens are a series of non-metal elements from group 17 of the periodic table (formerly VII). The halogens include fluorine (F), chlorine (Cl), bromine (Br), iodine (I), and astatine (At). The artificially created element 117 (ununseptium) may also be considered a halogen. Physical Properties Atoms get bigger down the group as additional electron shells are filled. When fluorine exists as a diatomic molecule, the F–F bond is unexpectedly weak. This is because fluorine atoms are the smallest of the halogens—the atoms are bonded close together, which leads to repulsion between free electrons in the two fluorine atoms. The boiling points of halogens increase down the group due to the increasing strength of Van der Waals forces as the size and relative atomic mass of the atoms increase.

This change manifests itself in a change in the phase of the elements from gas (F2, Cl2) to liquid (Br2), to solid (I2). The halogens are the only periodic table group containing elements in all three familiar states of matter (solid, liquid, and gas) at standard temperature and pressure . Halogens represents all of the three familiar states of matter: (left to right) chlorine is a gas, bromine is a liquid, and iodine is a solid. Highly reactive fluorine is not included in the picture. Chemical Properties Electronegativity is the ability of an atom to attract electrons or electron density towards itself within a covalent bond . Electronegativity depends upon the attraction between the nucleus and bonding electrons in the outer shell. This, in turn, depends on the balance between the number of protons in the nucleus, the distance between the nucleus and bonding electrons, and the shielding effect of inner electrons. In hydrogen halides (HX, where X is the halogen), the H-X bond gets longer as the halogen atoms get larger. This means the shared electrons are further from the halogen nucleus, which increases the shielding of inner electrons.

This means electronegativity decreases down the group. Halogens are highly reactive, and they can be harmful or lethal to biological organisms in sufficient quantities. This reactivity is due to high electronegativity and high effective nuclear charge. Halogens can gain an electron by reacting with atoms of other elements. Fluorine is one of the most reactive elements. It reacts with otherwise inert materials such as glass , and it forms compounds with the heavier noble gases . It is a corrosive and highly toxic gas. Fluorine's reactivity means that once it does react with something, it bonds so strongly that the resulting molecule is inert and non-reactive. Fluorine can react with glass in the presence of small amounts of water to form silicon tetrafluoride (SiF4). Thus fluorine must be handled with substances like the inert organofluorine compound Teflon.

Fluorine reacts vigorously with water to produce oxygen (O2) and hydrogen fluoride: $2 F_2 (g) + 2 H_2O (l) \rightarrow O_2 (g) + 4 HF (aq)$ Chlorine has maximum solubility of 7.1 g per kg of water at ambient temperature (21 °C). Dissolved chlorine reacts to form hydrochloric acid (HCl) and hypochlorous acid (HClO), a solution that can be used as a disinfectant or bleach: $Cl_2 (g) + H_2O (l) \rightarrow HCl (aq) + HClO (aq)$ Bromine has a solubility of 3.41 g per 100 g of water. It slowly reacts to form hydrogen bromide (HBr) and hypobromous acid (HBrO): $Br_2 (g) + H_2O (l) \rightarrow HBr (aq) + HBrO (aq)$ Iodine is minimally soluble in water, with a solubility of 0.03 g per 100 g water.

However, iodine will form an aqueous solution in the presence of iodide ion . This occurs with the addition of potassium iodide (KI), forming a triiodide ion. Chlorine, Chemical Element - reaction, water, uses, elements, metal, gas, number, name PRONUNCIATION CLOR-een Chlorine is a member of the halogen family. Halogens are the elements that make up Group 17 (VIIA) of the periodic table, a chart that shows how elements are related to one another. They include fluorine, bromine, iodine, and astatine. Chlorine is highly reactive, ranking only below fluorine in its chemical activity. Bleach is a common household item used to help clean clothes. Discovery and naming Chlorine compounds have been important to humans for thousands of years. Ordinary table salt, for example, is sodium chloride (NaCl). Still, chlorine was not recognized as an element until 1774, when Scheele was studying the mineral pyrolusite. Pyrolusite consists primarily of manganese dioxide (MnO 2 ).

Scheele mixed pyrolusite with hydrochloric acid (HCl), then called spiritus salis. He found that a greenish-yellow gas with a suffocating odor "most oppressive to the lungs" was released. The gas was chlorine. Scheele found that the new gas reacted with metals, dissolved slightly in water, and bleached flowers and leaves. He gave the gas the rather complex name of dephlogisticated marine acid. Chlorine occurs commonly both in the Earth's crust and in seawater. The true nature of Scheele's discovery was not completely understood for many years. Some chemists argued that his dephlogisticated marine acid was really a compound of a new element and oxygen. This confusion was finally cleared up in 1807. English chemist Sir Humphry Davy (1778-1829) proved that Scheele's substance was a pure element. He suggested the name chlorine for the element, from the Greek word chloros, Swedish pharmacist Carl Wilhelm Scheele. meaning "greenish-yellow." (See sidebar on Davy in the calcium entry.) Physical properties Chlorine is a dense gas with a density of 3.21 grams per liter.

By comparison, the density of air is 1.29 grams per liter. Chlorine changes from a gas into a liquid at a temperature of -34.05°C (-29.29°F) and from a liquid to a solid at -101.00°C (-149.80°F). The gas is soluble (dissolvable) in water. It also reacts chemically with water as it dissolves to form hydrochloric acid (HCl) and hypochlorous acid (HOCl). Chemical properties Chlorine is a very active element. It combines with all elements except the noble gases. The noble gases are the elements that make up Group 18 (VIIIA) of the periodic table. The reaction between chlorine and other elements can often be vigorous. For example, chlorine reacts explosively with hydrogen to form hydrogen chloride: Chlorine does not burn but, like oxygen, it helps other substances bum. Chlorine is a strong oxidizing agent (a chemical substance that gives up or takes on electrons from another substance). Occurrence in nature Chlorine occurs commonly both in the Earth's crust and in seawater.

Its abundance in the earth is about 100 to 300 parts per million. It ranks 20th among the elements in abundance in the earth. Its abundance in seawater is about 2 percent. The most common compound of chlorine in seawater is sodium chloride. Smaller amounts of potassium chloride also occur in seawater. The most common minerals of chlorine are halite, or rock salt (NaCl), sylvite (KCl), and camallite (KCl MgCl 2 ). Large amounts of these minerals are mined from underground salt beds that were formed when ancient oceans dried up. Over millions of years, the salts that remained behind were buried underground. They were also compacted (packed together) to form huge salt "domes." A salt dome is a large mass of salt found underground. Isotopes Two naturally occurring isotopes of chlorine exist, chlorine-35 and chlorine-36. Isotopes are two or more forms of an element. Isotopes differ from each other according to their mass number. The number written to the right of the element's name is the mass number. The mass number represents the number of protons plus neutrons in the nucleus of an atom of the element.

The number of protons determines the element, but the Chlorine combines with all elements except the noble gases. Here, it reacts with sodium. number of neutrons in the atom of any one element can vary. Each variation is an isotope. Seven radioactive isotopes of chlorine are known also. A radioactive isotope is one that breaks apart and gives off some form of radiation. Radioactive isotopes are produced when very small particles are fired at atoms. These particles stick in the atoms and make them radioactive. One radioactive isotope of chlorine is used in research. That isotope is chlorine-36. This isotope is used because compounds of chlorine occur so commonly in everyday life. The behavior of these compounds can be studied if chlorine-36 is used as a tracer. A tracer is an isotope whose presence in a material can be traced (followed) easily. For example, engineers are interested in knowing how seawater damages metals. This information is important in determining the best techniques to use in building ships. An experiment can be done by adding pieces of metal to seawater that contains radioactive chlorine-36. The sodium chloride in the seawater is changed slightly so that it contains radioactive chlorine instead of normal chlorine.

As the sodium chloride attacks the metal, its actions can be followed easily. The radioactive chlorine, chlorine-36, gives off radiation. That radiation can be detected by holding an instrument near the experiment. A scientist can find out exactly what happens when the sodium chloride attacks the metal. Extraction Chlorine is produced by passing an electric current through a water solution of sodium chloride or through molten (melted) sodium chloride. This process is one of the most important commercial processes in industry. The products formed include two of the most widely used materials: sodium hydroxide (NaOH) and chlorine (Cl 2 ). With a water solution, the reaction that occurs is: Hydrogen gas (H 2 ) is also formed in the reaction. Uses and compounds Chlorine is widely used throughout the world to purify water. In the United States, only about 6 percent of the chlorine manufactured is used in water purification. About three times as much is used in the paper and pulp industry as a bleach. The most important use of chlorine is to make other chemicals.

For example, chlorine can be combined with ethene, or ethylene, gas (C 2 )H 2 ), to make ethylene dichloride (C 2 )H 2 )Cl 2 ): Large amounts of chlorine minerals are mined from underground salt beds that were formed when ancient oceans dried up. About one-third of the chlorine produced in the United States goes to making ethylene dichloride. About 90 percent of ethylene dichloride goes to the manufacture of polyvinyl chloride (PVC). PVC is used to make piping, tubing, flooring, siding, film, coatings, and many other products. Ethylene dichloride has become one of the most popular products in American industry. About 4.5 billion kilograms (10 billion pounds) of the material are made each year. Who is getting poisoned? O ne of the most troubling uses of chlorine has been in making pesticides. A pesticide is a chemical used to kill pests. Pesticides have special names depending on the kind of pests they are designed to kill. Insecticides kill insects, rodenticides kill rodents (rats and mice), fungicides kill fungi, and nematicides kill worms. Certain chlorine compounds have become very popular as pesticides.

These compounds are called chlorinated hydrocarbons. They contain carbon, hydrogen, and chlorine. Probably the most famous chlorinated hydrocarbon is dichlorodiphenyltrichloroethane, or DDT. DDT was first prepared in 1873, but was not used as a pesticide until World War II (1939-45). Public health officials were at first delighted to learn that DDT kills disease-carrying insects very efficiently. There was great hope that DDT could be used to wipe out certain diseases in some parts of the world. Farmers were also excited about DDT. They found it could kill many of the pests that attacked crops. By the end of the 1950s, many farmers were spraying huge amounts of DDT on their land to get rid of pests. But problems began to appear. Many fish and birds in sprayed areas began to die or become deformed. Soon, these problems were traced to the use of DDT. The fish and birds ate insects that had been sprayed with DDT or drank water that contained DDT. It had a toxic effect on the fish and birds, just as it did on insects.

Bird populations declined drastically as DDT caused eggs to be so thin-shelled that young birds did not survive. Eventually, many governments began to ban the use of DDT. Since 1973, the United States has not allowed the compound to be used. It is still used in other nations of the world, however. These nations feel that the benefits of using DDT outweigh the harm it may cause. They feel that DDT can save lives by killing disease-causing pests. They know they can increase their food supplies by using DDT on crops. DDT is not the only chlorinated hydrocarbon used as a pesticide. Other compounds in this class include dieldrin, aldrin, heptachlor, and chlordan. The use of these compounds has also been banned or restricted in the United States. The U.S. government has decided the harm they cause to the environment is more important than the benefits they provide to farmers and other users. Another compound made using chlorine is propylene oxide (CH 3 CH0CH 2 ). There is no chlorine in propylene oxide, but chlorine is used in the process by which the compound is made. Propylene oxide is used to make a group of plastics known as polyesters.

Polyesters are found in a wide range of materials, including car and boat bodies, bowling balls, fabrics for clothing, and rugs. At one time, a large amount of chlorine was used to make a group of compounds known as chlorofluorocarbons (CFCs). CFCs are a family of chemical compounds containing carbon, fluorine, and chlorine. CFCs were once used in a wide variety of applications, such as air conditioning and refrigeration, aerosol spray products, and cleaning materials. They are now known to have serious environmental effects and have been banned from use in the United States and many other countries in the world. The reason for this ban is the damage caused by CFCs on the Earth's ozone layer. Ozone (O 3 ) is a form of oxygen that filters out harmful radiation from the sun. When CFCs escape into the atmosphere, they attack and destroy ozone molecules. They reduce the protection against radiation provided by ozone. Health effects Chlorine gas is extremely toxic. In small doses, it irritates the nose and throat. A person exposed to chlorine may experience sneezing, running nose, and red eyes. In larger doses, chlorine can be fatal.

In fact, chlorine gas was used during World War I (1914-18) by German armies as a weapon. Thousands of soldiers were killed or seriously wounded by breathing it. Those who survived gas attacks often were crippled for life. They were unable to breathe normally as a result of the damage to their throats and lungs. On the other hand, chlorine compounds are essential to plants. They become sick or die without it. In plants, chlorine is regarded as a micronutrient, which is a substance needed in very small amounts to maintain good health. Leaves turn yellow and die when plants get too little chlorine from the soil. Chlorine is produced by passing an electric current through a water solution of sodium chloride or through molten (melted) sodium chloride. Compounds of chlorine are important in maintaining good health in humans and animals. The average human body contains about 95 grams (about 3.5 ounces) of chlorine. Hydrochloric acid (HCl) in the stomach, for example, helps in the digestion of foods. Sodium chloride (NaCl) and potassium chloride (KCl) play an important role in the way nerve messages are sent throughout the body.

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Question: Chlorine, fluorine and bromine belong to which family of elements?
Answer: Halogens