Elements, Compounds and Mixtures

All substances are made of atoms - until now we called them particles. There are only about 100 different elements, but there are thousands of different chemicals. Most chemicals are made up of a combination of elements and we call these compounds. Two or more atoms joined together are known as a molecule.

	A substance that is made of only one sort of atom is called an __________
	__________ are made up of two or more elements held together by chemical bonds. All the molecules must be the same.
	__________ are a collection of different types of atoms and molecules that are not chemically bonded

All the elements (and nothing else) are shown in the periodic table. The columns are called __________, they contain elements with __________ chemical properties. Each element is represented by a chemical __________, normally from the latin for the element.

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Use the periodic table to fill in the symbols for the following elements:

Element	Symbol
Carbon	__________
Calcium	__________
Oxygen	__________
Hydrogen	__________

The formula of a compound shows the number and type of atoms that are joined together to make the compound. For example Water has the chemical formula H₂O. This means that it has two hydrogen atoms joined to one oxygen atom in each molecule.

Atoms themselves have a small central nucleus around which there are electrons orbiting:

		__________
		__________