Binary Compounds by Joining Elements Together

All the matter in the Universe is made up from just one hundred (approximately) elements. Everything you see around you is either elements, compounds or a mixture of these. All the compounds have been formed by these elements combining somehow over the years, some by direct contact and others by a series of devious routes. 

Most of the elements are metals. The first tools that were made by human beings were made of stone, because that is all they had. Eventually metals were discovered. The first metal to be discovered was probably gold. Gold can be found naturally in rocks as the metal, un-combined with anything else (this is called being found native )- Most metals are found combined with other elements as ores, which are compounds. 

There is a lot of oxygen in the atmosphere, and over the millions of years since the Earth was formed many metals have combined with oxygen to form compounds called oxides. Iron, for example, occurs in the molten core of our Earth, and is often found in the Earth s crust as the ore haematite, which is iron oxide. Iron oxide is a binary compound, which means it contains only two elements. Notice that its name ends with ide . This is true for all binary compounds. Metals tend to combine with non-metals. Where a binary compound is made up of a metal and a non-metal, the first name of the compound is simply the name of the metal it contains and the second is the name of the non-metal, changed to end in ide for example, the compound between copper and chlorine is copper chloride. 

In volcanic regions, natural un-combined sulfur is often found. Many metals have combined with this sulfur to form compounds called sulfides. Lead, for example, is often found as the ore galena, which is lead sulfide. The percentages of lead and sulfur in galena are always the same. 

Bronze contains two elements, but it is not a compound. The elements are both metals, namely copper and tin, but they are not chemically combined in bronze. Bronze is a mixture of metals, an alloy the two metals can be separated. The percentages of copper and tin in bronze can vary considerably, depending on how much of each you add together. The properties of bronze depend on the relative amounts of the two metals. Another very common alloy is brass (copper and zinc). In compounds, the ratio of the elements present is always the same value and fixed. 

---