IGCSE Online Tutorial - Jesmul Sir's Portal

# IGCSE Online Tutorial - Jesmul Sir's Portal

Atomic equations and Isotopes

## Atomic notation and equations

To help us to describe atoms and nuclei, we use numbers and letters. Here is an example:
The atom in the diagram is described by the numbers and letters shown next to it. All atoms of a certain element will have the same number of protons in the nucleus.

The top number is called the mass number or the nucleon number. It tells you how many particles are in the nucleus, i.e. how many protons and neutrons.

The bottom number is called the proton number or the atomic number. It tells you how many protons there are in the nucleus.

The letters give you a clue as to the name of the atom. This is an atom of 'helium', He.

The number of electrons in an atom is the same as the number of protons. That makes the atom neutral overall (neither negative nor positive).

If the numbers are not equal, the atom becomes a charged particle. We call these charged particles ions.

Now it's your turn to have a go. Using the diagrams, you should be able to tell what the missing numbers are.

Try typing them in the correct place and then check your answer.

Example 1: A Lithium Atom
You can also write equations for nuclear reactions. In these equations you will need to make sure that:

1. The total number of protons is the same before and after the reaction.
2. The total number of nucleons is the same before and after the reaction.
In this reaction, carbon and helium is combined to form oxygen.
Notice that if you add up the numbers at the top of each atom (the nucleon numbers) on the left hand side you get the same as the total for the numbers on the right hand side.

The same is true for the proton numbers.

Have a go at this one.