Atomic Structure

Atoms are made up of Protons, Neutrons and Electrons

Inside every atom, there's a nucleus containing protons and neutrons. Protons and neutrons are both known as nucleons. Orbiting this core are the electrons. This is the nuclear model of the atom.

The following are the properties of electrons, protons and neutrons in the table:

Atoms are Really, Really Tiny

Each atom is about a tenth of a nanometer (1 x 10^-10m) in diameter. To give you that in context, you'd need to line up around 4 million iron atoms side by side to give you a line 1 mm long. If you think that's small, try the nucleus.

1. Although the proton and neutron are 2000 times more massive than the electron, the nucleus only takes up a tiny proportion of the atom. The electrons orbit at relatively vast distances.
2. The nucleus is only 10 000th the size of the whole atom - most of the atom is empty space.
3. If we were to shrink the Solar System (including poor rejected Pluto) so the Sun was the size of a gold nucleus, Pluto would only be half as far away as gold's first electron.

Isotopes have the Same Proton Number, but Different Nucleon Numbers

Atoms with the same number of protons but different number of neutrons are called isotopes.

• Changing the number of neutrons doesn't affect the atom's chemical properties.
• The number of neutrons affects the stability of a nucleus though.
• In general, the greater the number of neutrons compared with the number of protons, the more unstable the nucleus.
• Unstable nuclei may be radioactive and decay to make themselves stable.

~The Nucleon Number is the Total Number of Protons and Neutrons.