Isotopes and relative atomic mass

First half of this, easy. Second half... maths. It's all just smoke and mirrors.

Learn this definition and that is the topic covered, easy stuff!

"Isotopes are: different atomic forms of the same element, which have the SAME number of PROTONS but DIFFERENT numbers of NEUTRONS."

For safety sake I will explain it. If something has 8 protons in its atomic number it should have 16 in its mass number. If it doesn't? DING DING DING. Those alarm bells. Could be an isotope.

Here comes the hard bit...open wide! Well that sounded a bit sexual. Moving on... The "Relative atomic mass" takes Isotopes into account. What a nice guy. You need to know 3 steps because they will give you the figures you need in the exam:

• Multiply the mass of each isotope by its relative abundance.
• Add those together
• Simply divide by the sum of the relative abundance.

I nicked this picture straight from the revision guide:

If you can read it, learn it.