Charges on Atoms
- What is an atom?
Atoms Part 1
Atoms part 2
Here is the picture of the helium atom which we saw in part 1. It shows 4 nucleons - 2 protons and 2 neutrons. Going around the outside are 2 electrons.
If you look closely, you can see a positive (+) sign on each of the protons, and a negative (-) sign on each of the electrons. Each proton in an atom has a positive charge, and each electron has a negative charge. This is true for every atom, not just helium atoms.
The charge is called an "electrostatic" charge. Electrons have a negative electrostatic charge and protons have a positive electrostatic charge.
These electrons are the same sort of electrons which carry charge in a battery, or the mains electricity. (Think of electronics!) When the charge isn't moving, it is called electrostatic. When it is moving, or flowing, it is called electric current. The current in a wire appears because a negative charge is being carried by electrons moving along it.
The charges on both the protons and the electrons are the same strength, but opposite to each other. The charge on a proton can be thought of as "+1"., and the charge on an electron is just the same strength, but is "-1". There is no charge on a neutron, so it has a charge of "0".
So, in any atom where there are the same number of protons and electrons, the atom will have a total charge of "0". The charge on every proton will be cancelled out by the opposite charge on each electron.
Atoms v Ions
Strictly speaking, every atom has an equal amount of protons and electrons, and so has no overall charge. That's because atoms which don't aren't called atoms at all - they are called ions!
If a neutral atom loses an electron (which is negatively charged), the overall charge is positive (because there are more protons than electrons). This positively charged atom is called a positive ion, or cation.
If a neutral atom gains an electron, they outnumber the protons, so the overall charge is negative. This negatively charged atom is called a negative ion, or anion.
- Protons have a positive charge of 1 (+1)
- Neutrons have a charge of 0
- Electrons have a negative charge of 1 (-1)
So atoms with equal amounts of protons and electrons have a total charge of "0"