Year 1084 (MLXXXIV) was a leap year starting on Monday (link will display the full calendar) of the Julian calendar.
Chromium
Chromium is a chemical element. Its symbol on the periodic table (a list of all the elements) is Cr. It always has 24 protons, so its atomic number is 24. Its mass number (number of protons and neutrons) is about 54. Most of the times it has 28 neutrons, but different isotopes have more or fewer neutrons. As a metal, it has 24 electrons. Its ions have fewer electrons.
Chromium is a shiny metal. It is reactive, but it reacts with air to produce a very thin coating of chromium(III) oxide, which prevents it from rusting any more.
Chromium occurs in several oxidation states; +2, +3, and +6 are most common. It forms chemical compounds that are colorful.
There are two main types of chromium ions, which are found in chromium compounds. One type of chromium ion ("Cr", trivalent chromium ) is required by our body and by those of other animals. If we do not get enough chromium, certain parts of our body may not work properly. We get most of the chromium we need from our food we eat. Chromium is also put into vitamins to make sure that we get enough. If we get too much of this type of chromium, it can harm our body.
Another type of chromium ("Cr" (chromate, hexavalent chromium), in the +6 oxidation state) can cause cancer or make people sick, even though most people do not get exposed to it much. It is found in places that make chromium metal, which is why they need to be cleaned up when they close. Hexavalent chromium can be destroyed by reacting it with reducing agents, turning it into Cr (trivalent chromium). They are strong oxidizing agents.
The chromate ion is CrO. Chromates are generally yellow.
The dichromate ion is CrO. Dichromates are red or orange.
Chromium occurs as chromite. Chromite is a mixture of iron(II) oxide and chromium(III) oxide. Its chemical formula is FeCrO. It is heated with sodium carbonate to make sodium chromate, iron(III) oxide, and carbon dioxide. The sodium chromate is reacted with sulfuric acid to produce sodium dichromate. The sodium dichromate is reduced by carbon to chromium(III) oxide. The chromium(III) oxide is reacted with aluminum to make chromium metal. The chromates and dichromates are what make chromium production areas toxic.
Chromium is used in different metal products. Stainless steel is the most common use. It is also used in "chrome plating", where it makes things shiny and stops corrosion. Some chromates were used as pigments, but they are toxic so people do not want to use them anymore.
Chromium metal is nontoxic. But hexavalent chromium is toxic and carcinogenic, and trivalent chromium is mildly toxic in large quantities.
Neon
Neon is a noble gas. It is chemical element 10 on the periodic table. Its symbol is Ne.
The word "neon" comes from the Greek word meaning "new". It was discovered by William Ramsay and Morris W. Travers in 1898.
Neon does not react with other elements, so it is found by itself. There is not much neon in the air, and it is clear, so we do not see it.
Neon gas is used in gas discharge lamps. When electricity goes through the neon, it lights up red. Due to this quality, it is used in signs. Similar signs use other gases to make other colors, but they are also often called "neon signs".
Neon is also a term referring to a type of color that is very bright, such as lime green.
No true chemical compounds including the neutral compounds of neon are known. Where there is the helium compound HHeF, which might be stable, the analogous compound with Neon is not.
Tin
Tin is a chemical element with symbol Sn (for ) and atomic number 50. It is in Group 14 on the periodic table. It is not radioactive.
Tin is a silver, somewhat soft metal. It is a post-transition metal. Its melting point is 231.93°C and its boiling point is 2602 °C. It can melt easily in a flame. It is malleable. It makes a crackling sound called tin cry when a piece of it is bent. Tin has more non-radioactive isotopes than any other element.
Tin is found in two allotropes: alpha-tin and beta-tin. Alpha-tin is a brittle, dull, powdery, semimetallic form of tin. It is made when very pure tin is cooled. Beta-tin is the normal shiny, soft, conductive, metallic form. It is made at higher temperatures. The decay of tin by turning from beta-tin to alpha-tin is called "tin pest". Alpha-tin is not wanted in many places. When small amounts of other elements like antimony are added, the tin cannot change into alpha-tin. When alpha-tin is heated, it changes into beta-tin.
Tin can be hardened by adding antimony or copper, as well as some other elements. These also make it resistant to tin pest. Tin can also be made very shiny. Tin can make an alloy with copper called bronze.
Tin resists many corrosive substances and is often used to protect other metals. Salt water and fresh water do not affect tin. It dissolves in strong acids to make tin salts. It reacts with some strong bases.
Tin forms chemical compounds in two oxidation states: +2 and +4. +2 compounds are reducing agents. Some of them are colorless while others are colored. +4 compounds are more unreactive and act more covalent.
Tin burns in air to make tin(IV) oxide, which is white. Tin(IV) oxide dissolves in acids to make other tin(IV) compounds. Tin(IV) chloride is a colorless fuming liquid when anhydrous and a white solid when hydrated. It easily reacts with water to make tin(IV) oxide and an acid again.
Tin reacts with hydrohalic acids to make tin(II) halides. For example, tin(II) chloride is made when tin dissolves in hydrochloric acid. Tin(IV) halides are made when tin reacts with the halogens. Tin(IV) chloride is made when tin reacts with chlorine. Tin(II) sulfate is different as it does not oxidize to tin(IV) sulfate. Tin(II) oxide is a blue-black solid that burns in air to make tin(IV) oxide.
+2 compounds are reducing agents. They are about as common as +4 compounds. Some are colorless, while others are colored.
+4 compounds are unreactive. Some are colorless.
Tin is not found as a metal in the ground. It is normally in the form of cassiterite. Cassiterite is a mineral containg tin(IV) oxide. The cassiterite is normally found downstream of the cassiterite deposit when it is by a stream or river. Tin is also found in some complicated sulfide minerals.
Tin does not have any major job in the human body.
Tin is made by heating cassiterite with carbon in a furnace. China is the biggest maker of tin.
People discovered tin long ago and used it with other metals. When copper and tin are mixed together, bronze is made. Bronze was important in the past, because it was one of the strongest metals available, which meant it was useful in weapons and tools. Bronze changed the world when it was first invented, starting the Bronze Age. People organized themselves more, because making tools from bronze was harder than making them from rock and wood like they did before.
Tin is used in solder. Solder used to contain a mixture of lead and tin. Now the lead is removed because of its toxicity.
Tin is also used to make pewter, which is mainly tin mixed with a small amount of copper and other metals. Babbitt metal also has tin in it. Tin is used to coat several metals, like lead and steel. Tin plated steel containers are used to store foods. The pipes on a pipe organ are made of tin. Tin foil was used before aluminium foil. Tin was one of the first superconductors to be found. Organotin compounds are more common than almost any other organometal compound. They are used in some PVC pipes to stop them from decaying. Organotin compounds are toxic, though.
Tin is not toxic, but tin compounds are very toxic to marine life. They are a little toxic to humans.
Silicon