# 1 From elements to compounds

Atoms of different elements can combine in a seemingly infinite variety of ways to form chemical compounds. Each one can be represented by a formula that shows how many atoms of each element there are in the compound.

Some examples of compounds and their constituent elements are given in Table 1.

## Table 1 The constituent elements of some selected chemical compounds.

Compound | Constituent elements | Compound | Constituent elements
--- | --- | --- | ---
sodium chloride | sodium, chlorine | calcium carbonate | calcium, carbon, oxygen
Water | hydrogen, oxygen | carbon dioxide | carbon, oxygen
sulfur dioxide | sulfur, oxygen | iron oxide | iron, oxygen
sulfuric acid | hydrogen, sulfur, oxygen | sodium hydroxide | Sodium, oxygen and hydrogen.

For some of the examples in this table, you may be thinking (not unreasonably) that the link between the compound and what elements it is made from is not clear.

A fair point.

However the structure and origin of the names and formulas of compounds will be the focus of this session’s study, which together with an introduction to chemical bonding and the useful concept of valency, should go a long way to addressing this point, and giving you a fundamental understanding of the nature of chemical compounds in general.

OpenLearn - Discovering chemistry
Except for third party materials and otherwise, this content is made available under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 Licence, full copyright detail can be found in the acknowledgements section. Please see full copyright statement for details.