Chemistry Revision.

Element Facts:

Around 100 elements. All atoms are the same in the element.

Compound Facts:

Compounds contain two or more different elements chemically combined in a fixed number. Usually have totally different properties to the elements that they're made from. To seperate a compound into an element you need to mae a chemical reaction.

Mixture Facts:

In a mixture you have different elements or compounds not chemically combined together. Use physical techniques to separate a mixture.

Interpreting a chemical formula:

Examples:MgS - Mg stands for Magnesium, S stands for Sulfur.No numbers mean you have 1x Magnesium and 1x Sulfur. Na2SO4 - Na stands for Sodium, S stands for Sulfur and O stands for Oxygen.The 2 after the Na means you have 2x Sodium and the 4 after the O means there are 4x Oxygen. Na2SO4 - Stands for Sodium Sulfate, whereas Na2SO3 stands for Sodium Sulfite. Ca(OH)2 - Ca stands for Calcium, O stands for Oxygen and the H stands for Hydrogen. 1x Calcium and 2x Oxygen and Hydrogen.