Atomic Structure

What is an Atom?

Everything is made of atoms.
An atom is the smallest piece of a substance that can exist.
7 million atoms joined together in a straight line
would be about 1mm long.

All atoms have a nucleus (the big bit in the middle).
The nucleus contains protons and neutrons.

All atoms have electrons.
For any atom, the number of protons
is the same as the number of electrons.
If an atom loses or gains electrons it is called an ion.

This is a picture of a sodium atom.
It has 11 protons, 11 electrons and 12 neutrons.

The electron structure is 2, 8, 1.

Each proton has an electrical charge of +1.
Each electron has an electrical charge of -1.
The neutron has no charge (it is neutral).
An atom has the same number of protons and electrons
so the overall charge is zero (it is neutral).
The mass of a neutron and a proton are the same.

An electron is very much smaller,
about 1÷2000 times the size of a proton
although it has an equal and opposite electrical charge.
The electrons, although tiny
take up most of the space of an atom.
This means that most of the space of an atom
contains hardly any mass. It is mostly empty space
with nearly all the mass centred at the nucleus.

Summary

The protons, neutrons and electrons
are shown as coloured to distinguish them from each other.
In reality they have no colour.

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