Atoms and Elements 02

This KS3 Science quiz will quiz you on atoms and elements. In 1661, Robert Boyle defined an element as a substance that could not be broken down into a simpler substance. At the start of the 20^th century, scientists discovered that elements were made up from atoms which could be split into protons, neutrons and electrons. Now, we say that an element is a substance that contains only one type of atom. Each of the different atoms has a name and a chemical symbol. A chemical symbol always starts with a capital letter and is followed by either zero, one or two small letters e.g. I and Ir stand for iodine and iridium.

Chemical formulae are a quick way of writing down information about chemical substances - Cu is the shorthand for 'here we have one single atom of the element copper'.

The formula for water is H₂O. Water is therefore not an element as it contains two different atoms - two atoms of hydrogen and one of oxygen. If there is no little number after a chemical symbol, it means there is only ONE atom. So in the formula H₂SO₄, there are 2 atoms of hydrogen (there is a small number 2 AFTER the symbol), only one atom of sulfur (there is NO small number after the symbol for sulfur) and 4 atoms of oxygen (can you see why?).