JK-TK/Newdata huggingface dataset:
Put three drops of phenolphthalein indicator. Put about 0.5g of Lithium metal into the beaker. Determine the pH of final product Repeat the experiment using about 0.1 g of Sodium and Potassium. Caution: Keep a distance Observations Alkali metal Observations Comparative speed/rate of the reaction Lithium -Metal floats in water -rapid effervescence/fizzing/bubbling -colourless gas produced (that extinguishes burning splint with explosion /“pop” sound) -resulting solution turn phenolphthalein indicator pink -pH of solution = 12/13/14 Moderately vigorous Sodium -Metal floats in water -very rapid effervescence /fizzing /bubbling -colourless gas produced (that extinguishes burning splint with explosion /“pop” sound) -resulting solution turn Very vigorous
31 phenolphthalein indicator pink -pH of solution = 12/13/14 Potassium -Metal floats in water -explosive effervescence /fizzing /bubbling -colourless gas produced (that extinguishes burning splint with explosion /“pop” sound) -resulting solution turn phenolphthalein indicator pink -pH of solution = 12/13/14 Explosive/burst into flames Explanation Alkali metals are less dense than water. They therefore float in water.They react with water to form a strongly alkaline solution of their hydroxides and producing hydrogen gas. The rate of this reaction increase down the group. i.e. Potassium is more reactive than sodium .Sodium is more reactive than Lithium. The reactivity increases as electropositivity increases of the alkali increases. This is because as the atomic radius increases , the ease of donating/losing outer electron increase during chemical reactions.
Potassium is more reactive than sodium .Sodium is more reactive than Lithium. The reactivity increases as electropositivity increases of the alkali increases. This is because as the atomic radius increases , the ease of donating/losing outer electron increase during chemical reactions. Chemical equations 2Li(s) + 2H2O(l) -> 2LiOH(aq) + H2(g) 2Na(s) + 2H2O(l) -> 2NaOH(aq) + H2(g) 2K(s) + 2H2O(l) -> 2KOH(aq) + H2(g) 2Rb(s) + 2H2O(l) -> 2RbOH(aq) + H2(g) 2Cs(s) + 2H2O(l) -> 2CsOH(aq) + H2(g) 2Fr(s) + 2H2O(l) -> 2FrOH(aq) + H2(g) Reactivity increase down the group (iv) Reaction with chlorine: Experiment Cut about 0.5g of sodium into a deflagrating spoon with a lid cover. Introduce it on a Bunsen flame until it catches fire. Quickly and carefully lower it into a gas jar containing dry chlorine to cover the gas jar. Repeat with about 0.5g of Lithium. Caution: This experiment should be done in fume chamber because chlorine is poisonous /toxic. Observation Sodium metal continues to burn with a yellow flame forming white solid/fumes. 32 Lithium metal continues to burn with a crimson flame forming white solid / fumes. Alkali metal react with chlorine gas to form the corresponding metal chlorides. The reactivity increase as electropositivity increase down the group from Lithium to Francium.The ease of donating/losing the outer electrons increase as the atomic radius increase and the outer electron is less attracted to the nucleus.
32 Lithium metal continues to burn with a crimson flame forming white solid / fumes. Alkali metal react with chlorine gas to form the corresponding metal chlorides. The reactivity increase as electropositivity increase down the group from Lithium to Francium.The ease of donating/losing the outer electrons increase as the atomic radius increase and the outer electron is less attracted to the nucleus. Chemical equations 2Li(s) + Cl2(g) -> 2LiCl(s) 2Na(s) + Cl2(g) -> 2NaCl(s) 2K(s) + Cl2(g) -> 2KCl(s) 2Rb(s) + Cl2(g) -> 2RbCl(s) 2Cs(s) + Cl2(g) -> 2CsCl(s) 2Fr(s) + Cl2(g) -> 2FrCl(s) Reactivity increase down the group The table below shows some compounds of the 1st three alkali metals Some uses of alkali metals include: (i)Sodium is used in making sodium cyanide for extracting gold from gold ore. (ii)Sodium chloride is used in seasoning food. (iii)Molten mixture of sodium and potassium is used as coolant in nuclear reactors. (iv)Sodium is used in making sodium hydroxide used in making soapy and soapless detergents.
(ii)Sodium chloride is used in seasoning food. (iii)Molten mixture of sodium and potassium is used as coolant in nuclear reactors. (iv)Sodium is used in making sodium hydroxide used in making soapy and soapless detergents. Lithium sodium Potassium Hydroxide LiOH NaOH KOH Oxide Li2O Na2O K2O Sulphide Li2S Na2S K2S Chloride LiCl NaCl KCl Carbonate Li2CO3 Na2CO3 K2CO3 Nitrate(V) LiNO3 NaNO3 KNO3 Nitrate(III) - NaNO2 KNO2 Sulphate(VI) Li2SO4 Na2SO4 K2SO4 Sulphate(IV) - Na2SO3 K2SO3 Hydrogen carbonate - NaHCO3 KHCO3 Hydrogen sulphate(VI) - NaHSO4 KHSO4 Hydrogen sulphate(IV) - NaHSO3 KHSO3 Phosphate - Na3PO4 K3PO4 Manganate(VI) - NaMnO4 KMnO4 Dichromate(VI) - Na2Cr2O7 K2Cr2O7 Chromate(VI) - Na2CrO4 K2CrO4
33 (v)Sodium is used as a reducing agent for the extraction of titanium from Titanium(IV)chloride. (vi)Lithium is used in making special high strength glasses (vii)Lithium compounds are used to make dry cells in mobile phones and computer laptops. Group II elements: Alkaline earth metals Group II elements are called Alkaline earth metals . The alkaline earth metals include: Element Symbol Atomic number Electron structure Oxidation state Valency Beryllium Be 4 2:2 Be2+ 2 Magnesium Mg 12 2:8:2 Mg2+ 2 Calcium Ca 20 2:8:8:2 Ca2+ 2 Strontium Sr 38 2:8:18:8:2 Sr2+ 2 Barium Ba 56 2:8:18:18:8:2 Ba2+ 2 Radium Ra 88 2:8:18:32:18:8:2 Ra2+ 2 All alkaline earth metal atoms have two electrons in the outer energy level. They therefore are divalent.
Group II elements: Alkaline earth metals Group II elements are called Alkaline earth metals . The alkaline earth metals include: Element Symbol Atomic number Electron structure Oxidation state Valency Beryllium Be 4 2:2 Be2+ 2 Magnesium Mg 12 2:8:2 Mg2+ 2 Calcium Ca 20 2:8:8:2 Ca2+ 2 Strontium Sr 38 2:8:18:8:2 Sr2+ 2 Barium Ba 56 2:8:18:18:8:2 Ba2+ 2 Radium Ra 88 2:8:18:32:18:8:2 Ra2+ 2 All alkaline earth metal atoms have two electrons in the outer energy level. They therefore are divalent. They donate /lose the two outer electrons to have oxidation state M2+ The number of energy levels increases down the group from Beryllium to Radium. The more the number of energy levels the bigger/larger the atomic size. e.g. The atomic size/radius of Calcium is bigger/larger than that of Magnesium because Calcium has more/4 energy levels than Magnesium (3 energy levels). Atomic radius and ionic radius of alkaline earth metals increase down the group as the number of energy levels increases. The atomic radius of alkaline earth metals is bigger than the ionic radius. This is because they react by losing/donating the two outer electrons and hence lose the outer energy level. Table showing the atomic and ionic radius of the 1st three alkaline earth metals Element Symbol Atomic number Atomic radius(nM) Ionic radius(nM) Beryllium Be 4 0.089 0.031 Magnesium Mg 12 0.136 0.065
34 Calcium Ca 20 0.174 0.099 The atomic radius of Magnesium is 0.136nM .The ionic radius of Mg2+ is 0.065nM. This is because Magnesium reacts by donating/losing the two outer electrons and hence the outer energy level. The remaining electrons/energy levels experience more effective / greater nuclear attraction/pull towards the nucleus reducing the atomic radius. Electropositivity All alkaline earth metals are also electropositive like alkali metals. The electropositivity increase with increase in atomic radius/size.
The remaining electrons/energy levels experience more effective / greater nuclear attraction/pull towards the nucleus reducing the atomic radius. Electropositivity All alkaline earth metals are also electropositive like alkali metals. The electropositivity increase with increase in atomic radius/size. Calcium is more electropositive than Magnesium. This is because the effective nuclear attraction on outer electrons decreases with increase in atomic radius. The two outer electrons in calcium experience less nuclear attraction and can be lost/ donated easily/with ease because of the higher/bigger atomic radius. Ionization energy For alkaline earth metals the 1st ionization energy decrease down the group as the atomic radius increase and the effective nuclear attraction on outer energy level electrons decrease. e.g. The 1st ionization energy of Magnesium is 900 kJmole-1 while that of Calcium is 590 kJmole-1 .This is because atomic radius increase and thus effective nuclear attraction on outer energy level electrons decrease down the group from magnesium to calcium. It requires therefore less energy to donate/lose outer electron in calcium than in magnesium. The minimum amount of energy required to remove a second electron from an ion of an element in its gaseous state is called the 2nd ionization energy. The 2nd ionization energy is always higher /bigger than the 1st ionization energy. This because once an electron is donated /lost form an atom, the overall effective nuclear attraction on the remaining electrons/energy level increase. Removing a second electron from the ion require therefore more energy than the first electron. The atomic radius of alkali metals is higher/bigger than that of alkaline earth metals.This is because across/along the period from left to right there is an increase in nuclear charge from additional number of protons and still additional number of electrons entering the same energy level. Increase in nuclear charge increases the effective nuclear attraction on the outer energy level which pulls it closer to the nucleus. e.g. Atomic radius of Sodium (0.157nM) is higher than that of Magnesium (0.137nM). This is because Magnesium has more effective nuclear attraction on
35 the outer energy level than Sodium hence pulls outer energy level more nearer to its nucleus. Physical properties Soft/Easy to cut: Alkaline earth metals are not soft and easy to cut with a knife like alkali metals.
Atomic radius of Sodium (0.157nM) is higher than that of Magnesium (0.137nM). This is because Magnesium has more effective nuclear attraction on
35 the outer energy level than Sodium hence pulls outer energy level more nearer to its nucleus. Physical properties Soft/Easy to cut: Alkaline earth metals are not soft and easy to cut with a knife like alkali metals. This is because of the decrease in atomic radius of corresponding alkaline earth metal, increases the strength of metallic bond and the packing of the metallic structure. Alkaline earth metals are (i)ductile(able to form wire/thin long rods) (ii)malleable(able to be hammered into sheet/long thin plates) (iii)have high tensile strength(able to be coiled without breaking/ not brittle/withstand stress) Appearance: Alkali earth metals have a shiny grey metallic luster when their surface is freshly polished /scrubbed. The surface slowly tarnishes on exposure to air. This is because the metal surface slowly undergoes oxidation to form an oxide. This oxide layer should be removed before using the alkaline earth metals. Melting and boiling points: Alkaline earth metals have a relatively high melting/ boiling point than alkali metals. This is because alkali metals use only one delocalized electron to form a weaker metallic bond/structure. Alkaline earth metals use two delocalized electrons to form a stronger metallic bond /structure. The melting and boiling points decrease down the group as the atomic radius/size increase reducing the strength of metallic bond and packing of the metallic structure. e.g. Beryllium has a melting point of 1280oC. Magnesium has a melting point of 650oC.Beryllium has a smaller atomic radius/size than magnesium .The strength of metallic bond and packing of the metallic structure is thus stronger in beryllium. Electrical/thermal conductivity: Alkaline earth metals are good thermal and electrical conductors. The two delocalized valence electrons move randomly within the metallic structure. Electrical conductivity increase down the group as the atomic radius/size increase making the delocalized outer electrons less attracted to nucleus. Alkaline earth metals are better thermal and electrical conductors than alkali metals because they have more/two outer delocalized electrons.e.g. Magnesium is a better conductor than sodium because it has more/two delocalized electrons than sodium.
Electrical conductivity increase down the group as the atomic radius/size increase making the delocalized outer electrons less attracted to nucleus. Alkaline earth metals are better thermal and electrical conductors than alkali metals because they have more/two outer delocalized electrons.e.g. Magnesium is a better conductor than sodium because it has more/two delocalized electrons than sodium. The more delocalized electrons the better the electrical conductor. 36 Calcium is a better conductor than magnesium. Calcium has bigger/larger atomic radius than magnesium because the delocalized electrons are less attracted to the nucleus of calcium and thus more free /mobile and thus better the electrical conductor Summary of some physical properties of the 1st three alkaline earth metals Alkaline earth metal Appearance Ease of cutting Melting point (oC) Boiling point (oC) Conduct- ivity 1st ionization energy 2nd ionization energy Beryllium Shiny grey Not easy 1280 3450 Good 900 1800 Magnesium Shiny grey Not Easy 650 1110 Good 736 1450 calcium Shiny grey Not easy 850 1140 Good 590 970 Chemical properties (i)Reaction with air/oxygen On exposure to air, the surface of alkaline earth metals is slowly oxidized to its oxide on prolonged exposure to air. Example On exposure to air, the surface of magnesium ribbon is oxidized to form a thin film of Magnesium oxide . 2Mg(s) + O2(g) -> 2MgO(s) (ii)Burning in air/oxygen Experiment Hold a about 2cm length of Magnesium ribbon on a Bunsen flame. Stop heating when it catches fire/start burning. Caution: Do not look directly at the flame Put the products of burning into 100cm3 beaker. Add about 5cm3 of distilled water. Swirl. Test the mixture using litmus papers. Repeat with Calcium Observations -Magnesium burns with a bright blindening flame -White solid /ash produced -Solid dissolves in water to form a colourless solution -Blue litmus paper remain blue -Red litmus paper turns blue -colourless gas with pungent smell of urine Explanation Magnesium burns in air with a bright blindening flame to form a mixture of Magnesium oxide and Magnesium nitride.
Swirl. Test the mixture using litmus papers. Repeat with Calcium Observations -Magnesium burns with a bright blindening flame -White solid /ash produced -Solid dissolves in water to form a colourless solution -Blue litmus paper remain blue -Red litmus paper turns blue -colourless gas with pungent smell of urine Explanation Magnesium burns in air with a bright blindening flame to form a mixture of Magnesium oxide and Magnesium nitride. 37 2Mg (s) + O2(g) -> 2MgO(s) 3Mg (s) + N2 (g) -> Mg3N2 (s) Magnesium oxide dissolves in water to form magnesium hydroxide. MgO(s) + H2O (l) -> Mg(OH)2(aq) Magnesium nitride dissolves in water to form magnesium hydroxide and produce ammonia gas. Mg3N2 (s) + 6H2O(l) -> 3Mg(OH)2(aq) + 2NH3 (g) Magnesium hydroxide and ammonia are weakly alkaline with pH 8/9/10/11 and turns red litmus paper blue. Calcium burns in air with faint orange/red flame to form a mixture of both Calcium oxide and calcium nitride. 2Ca (s) + O2(g) -> 2CaO(s) 3Ca (s) + N2 (g) -> Ca3N2 (s) Calcium oxide dissolves in water to form calcium hydroxide. CaO(s) + H2O(l) -> Ca(OH)2(aq) Calcium nitride dissolves in water to form calcium hydroxide and produce ammonia gas. Ca3N2 (s) + 6H2O(l) -> 3Ca(OH)2(aq) + 2NH3 (g) Calcium hydroxide is also weakly alkaline solution with pH 8/9/10/11 and turns red litmus paper blue. (iii)Reaction with water Experiment Measure 50 cm3 of distilled water into a beaker. Scrub/polish with sand paper 1cm length of Magnesium ribbon Place it in the water. Test the product-mixture with blue and red litmus papers. Repeat with Calcium metal. Observations -Surface of magnesium covered by bubbles of colourless gas. -Colourless solution formed.
Repeat with Calcium metal. Observations -Surface of magnesium covered by bubbles of colourless gas. -Colourless solution formed. -Effervescence/bubbles/fizzing takes place in Calcium. -Red litmus paper turns blue. -Blue litmus paper remains blue. Explanations Magnesium slowly reacts with cold water to form Magnesium hydroxide and bubbles of Hydrogen gas that stick on the surface of the ribbon. Mg(s) + 2H2O (l) -> Mg(OH)2(aq) + H2 (g)
38 Calcium moderately reacts with cold water to form Calcium hydroxide and produce a steady stream of Hydrogen gas. Ca(s) + 2H2O (l) -> Ca(OH)2(aq) + H2 (g) (iv)Reaction with water vapour/steam Experiment Put some cotton wool soaked in water/wet sand in a long boiling tube. Coil a well polished magnesium ribbon into the boiling tube. Ensure the coil touches the side of the boiling tube. Heat the cotton wool/sand slightly then strongly heat the Magnesium ribbon . Set up of apparatus Observations -Magnesium glows red hot then burns with a blindening flame. -Magnesium continues to glow/burning even without more heating. -White solid/residue. -colourless gas collected over water. Explanation On heating wet sand, steam is generated which drives out the air that would otherwise react with /oxidize the ribbon. Magnesium burns in steam/water vapour generating enough heat that ensures the reaction goes to completion even without further heating. White Magnesium oxide is formed and hydrogen gas is evolved. To prevent suck back, the delivery tube should be removed from the water before heating is stopped at the end of the experiment. Mg(s) + H2O (l) -> MgO(s) + H2 (g)
39 (v)Reaction with chlorine gas. Experiment Lower slowly a burning magnesium ribbon/shavings into a gas jar containing Chlorine gas. Repeat with a hot piece of calcium metal. Observation -Magnesium continues to burn in chlorine with a bright blindening flame. -Calcium continues to burn for a short time. -White solid formed . -Pale green colour of chlorine fades. Explanation Magnesium continues to burn in chlorine gas forming white magnesium oxide solid. Mg(s) + Cl2 (g) -> MgCl2 (s) Calcium burns slightly in chlorine gas to form white calcium oxide solid.
-Pale green colour of chlorine fades. Explanation Magnesium continues to burn in chlorine gas forming white magnesium oxide solid. Mg(s) + Cl2 (g) -> MgCl2 (s) Calcium burns slightly in chlorine gas to form white calcium oxide solid. Calcium oxide formed coat unreacted Calcium stopping further reaction Ca(s) + Cl2 (g) -> CaCl2 (s) (v)Reaction with dilute acids. Experiment Place about 4.0cm3 of 0.1M dilute sulphuric(VI)acid into a test tube. Add about 1.0cm length of magnesium ribbon into the test tube. Cover the mouth of the test tube using a thumb. Release the gas and test the gas using a burning splint. Repeat with about 4.0cm3 of 0.1M dilute hydrochloric/nitric(V) acid. Repeat with 0.1g of Calcium in a beaker with all the above acid Caution: Keep distance when using calcium Observation -Effervescence/fizzing/bubbles with dilute sulphuric(VI) and nitric(V) acids -Little Effervescence/fizzing/bubbles with calcium and dilute sulphuric(VI) acid. -Colourless gas produced that extinguishes a burning splint with an explosion/ “pop” sound. -No gas is produced with Nitric(V)acid. -Colourless solution is formed. Explanation Dilute acids react with alkaline earth metals to form a salt and produce hydrogen gas. Nitric(V)acid is a strong oxidizing agent. It quickly oxidizes the hydrogen produced to water. Calcium is very reactive with dilute acids and thus a very small piece of very dilute acid should be used.
Nitric(V)acid is a strong oxidizing agent. It quickly oxidizes the hydrogen produced to water. Calcium is very reactive with dilute acids and thus a very small piece of very dilute acid should be used. Chemical equations
40 Mg(s) + H2SO4 (aq) -> MgSO4(aq) + H2 (g) Mg(s) + 2HNO3 (aq) -> Mg(NO3)2(aq) + H2 (g) Mg(s) + 2HCl (aq) -> MgCl2(aq) + H2 (g) Ca(s) + H2SO4 (aq) -> CaSO4(s) + H2 (g) (insoluble CaSO4(s) coat/cover Ca(s)) Ca(s) + 2HNO3 (aq) -> Ca(NO3)2(aq) + H2 (g) Ca(s) + 2HCl (aq) -> CaCl2(aq) + H2 (g) Ba(s) + H2SO4 (aq) -> BaSO4(s) + H2 (g) (insoluble BaSO4(s) coat/cover Ba(s)) Ba(s) + 2HNO3 (aq) -> Ba(NO3)2(aq) + H2 (g) Ba(s) + 2HCl (aq) -> BaCl2(aq) + H2 (g) The table below shows some compounds of some alkaline earth metals Some uses of alkaline earth metals include: (i)Magnesium hydroxide is a non-toxic/poisonous mild base used as an anti acid medicine to relieve stomach acidity. (ii)Making duralumin. Duralumin is an alloy of Magnesium and aluminium used for making aeroplane bodies because it is light. (iii) Making plaster of Paris-Calcium sulphate(VI) is used in hospitals to set a fractures bone. (iii)Making cement-Calcium carbonate is mixed with clay and sand then heated to form cement for construction/building. (iv)Raise soil pH-Quicklime/calcium oxide is added to acidic soils to neutralize and raise the soil pH in agricultural farms. (v)As nitrogenous fertilizer-Calcium nitrate(V) is used as an agricultural fertilizer because plants require calcium for proper growth.
(iii)Making cement-Calcium carbonate is mixed with clay and sand then heated to form cement for construction/building. (iv)Raise soil pH-Quicklime/calcium oxide is added to acidic soils to neutralize and raise the soil pH in agricultural farms. (v)As nitrogenous fertilizer-Calcium nitrate(V) is used as an agricultural fertilizer because plants require calcium for proper growth. Beryllium Magnesium Calcium Barium Hydroxide Be(OH)2 Mg(OH)2 Ca(OH)2 Ba(OH)2 Oxide BeO MgO CaO BaO Sulphide - MgS CaS BaS Chloride BeCl2 MgCl2 CaCl2 BaCl2 Carbonate BeCO3 MgCO3 CaCO3 BaCO3 Nitrate(V) Be(NO3)2 Mg(NO3)2 Ca(NO3)2 Ba(NO3)2 Sulphate(VI) BeSO4 MgSO4 CaSO4 BaSO4 Sulphate(IV) - - CaSO3 BaSO3 Hydrogen carbonate - Mg(HCO3)2 Ca(HCO3)2 - Hydrogen sulphate(VI) - Mg(HSO4)2 Ca(HSO4)2 -
41 (vi)In the blast furnace-Limestone is added to the blast furnace to produce more reducing agent and remove slag in the blast furnace for extraction of Iron. (c)Group VII elements: Halogens Group VII elements are called Halogens. They are all non metals. They include: Element Symbol Atomic number Electronicc configuration Charge of ion Valency State at Room Temperature Fluorine Chlorine Bromine Iodine Astatine F Cl Br I At 9 17 35 53 85 2:7 2:8:7 2:8:18:7 2:8:18:18:7 2:8:18:32:18:7 F- Cl- Br- I- At- 1 1 1 1 1 Pale yellow gas Pale green gas Red liquid Grey Solid Radioactive All halogen atoms have seven electrons in the outer energy level. They acquire/gain one electron in the outer energy level to be stable. They therefore are therefore monovalent .They exist in oxidation state X- The number of energy levels increases down the group from Fluorine to Astatine. The more the number of energy levels the bigger/larger the atomic size. e.g.