There are four fundamental forces of nature.

Charge is the property that causes of one of them to act: the electrostatic force.

Up to GCSE the only particles that we are aware of that have charge are:

the proton (positive) and

the electron (negative).

After GCSE we will come across other particles that have charge - but we do not have to worry about them yet.

At A level we find out that muons are heavy electrons (negative) and quarks have partial charges – multiples of a third… so particles made up of them can have a net charge also.

They both experience a force.

Those with the same sign of charge repel each other

and those with the opposite sign of charge attract each other.

Like repel - opposites attract.

This force comes into effect when they interact by exchanging an ‘exchange particle’ – a photon

An atom is the smallest chemically indivisible particle of an element.

It is made up of a nucleus (containing protons and neutrons) orbited by electrons.

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It is the number of protons within the nucleus of the atom.

For atoms of a given element the proton number is always the same. The periodic table lists the elements in the order of their proton number.

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Chemists call the proton number the atomic number.

The total of the number of nucleons within the nucleus. It equals the sum of the protons and neutrons in the nucleus.

This will be different for each isotope of an element.

A neutral particle that is found in the nucleus of an atom.

It has the symbol 'n' and has roughly the same mass as a proton but no charge.

At advanced level you will find out it contains three quarks - d,d,u (two downs and an up!).

A positively charged particle that is found in the nucleus of an atom.

It has the symbol 'p' and is roughly the same mass as a neutron.

It has the same sized charge as an electron but opposite in sign.

At advanced level you will find out it contains three quarks - d,u,u (two ups and a down!).

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A negatively charged particle that is found orbiting the nucleus of an atom.

It has the symbol 'e' and is roughly a two thousandth of the mass of a proton or neutron.

It has the same sized charge as a proton but opposite in sign.

A negatively charged ion.

It is an atom that has gained electrons. Halogens form anions when they undergo chemical reactions. They do this to gain a full outer shell of electrons to increase their stability. They do this by adding an electron to their outermost shell which is only one short.

A positively charged ion.

It is an atom that has lost electrons. Alkali metals form cations when they undergo chemical reactions. They do this to gain a full outer shell of electrons to increase their stability. They do this by losing the single electron in their outermost shell.

1. The charge on each particle. The bigger the charges involved the stronger the force will be.

2. The distance between the charged objects. The further away from each other they are the smaller the force will be.

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3. The sign of the charges - if they are the same they will repel - if they are opposite they will attract.

Negative (gained electrons)

You can remember this by thinking that polythene has an 'n' in it.

Positive (lost electrons).

You can remember this as there is no 'n' in acetate - polythene and acetate are the only two you would be expected to recall.

Gravitational force (due to the object's mass) and electrostatic force (due to the object's charge).

These two forces are independent and whether you see the effect of charge depends on the mass of an object - because if its mass is large the force from the charge will not be evident because weight will 'win'.