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The nucleus is in the middle of the atom, like
the diagram suggests.
It contains two types of particles know as
Protons and Neutrons.
Overall the nucleus has a positive charge,
this is because protons have a positive
charge and neutrons have a neutral charge so
they have to have a positive charge.
The third type of particle included with the
atom are electrons, they orbit around the
In atom, if you know how many electrons are orbiting the nucleus you
know how many protons there are within the nucleus, as the number of
electrons = the number of protons.
The electrons are negatively charged.
Electrons also have virtually no mass and our in shells surrounding the
Because an atom contains equal numbers of protons and electrons, the
overall charge of an atom is exactly zero.
We can sum this up into a little table, which you should definitely know for
the exam .
Particle Mass Charge
Proton 1 +1
Neutron 1 0
Electron Very small 1
The atomic number is another way of saying how many protons are in
Each element has a different atomic number, so in the exam if you are
asked which element has 16 as its atomic number you need to look on
the periodic table and see that it is sulphur.
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Is the total number of protons and neutrons
The mass number is always bigger than the atomic number, normally
double the atomic number. This means that there are normally the same
amount of protons and neutrons in any atom.…read more