Atoms

The Neucleus:

1) it's in the middle of the atom

2) it contains protons and neutrons

3) it has a positive charge because of the protons

4) almost the whole mass of the atom is concentrated in the neucleus.

The electrons:

1) move around the neucleus in electron shells

2) they're negatively charged

3) they're tiny, but they cover a lot of space

4) the volume of their orbits determines the size of the atom - atoms have a radius of about 10 to the minus 10 m

5) electrons have virtually no mass

The number of protons equals the number of electrons

…