C4 Science

The Nucleus

• It's in the middle of the atom
• It contains protons and neutrons
• It has a positive charge because of the protons.
• Almost the whole mass of the atom is concentrated in the nucleus
• But size-wize it's tiny compared to the rest of the atom

The Electrons

• Move around the nucleus
• They're negatively charged.
• They're tiny, but they cover a lot of space.
• The volume of their orbits determines how big the atom is.
• They have virtually no mass
• They're arranged in shells around the nucleus

Particles

•  Protons are heavy and postively charged
• Neutrons are heavy and neutral
• Electrons are tiny and negatively charged

The number of Protons Equals number of Electrons

• Neutral atoms have no charged overall
• The charge on the electrons is the same as the charge on the protons - but opposite.
• This means the number f protons always equals the number of electrons in a neutral atom.
• If some electrons are added or removed, the atom becomes charged and is then an ion
• The number of neutrons isn't fixed but is usually about the same as the number of protons

Atoms of the same element all have the same number of protons - and atoms of different elements will have different numbers of protons.