Atomic Theory and Those Involved

Who were the people that developed the current theory of the atom?

John Dalton: suggested that particles that make up matter are like small, hard spheres that are different for different elements.
- All matter is made of small particles called atoms.
- Atoms cannot be created, destroyed, or divided into smaller particles.
- All atoms of the same element are identical in mass and size, but they are different in mass and size from the atoms of other elements.
- Compounds are created when atoms of different elements link together in definite proportions.

J.J. Thomson:
- Discovered that electrons are negatively charged particles and all atoms have them.
- Proposed the raisin bun model of the atom that had a positively charged ball like a bun with negatively charged particles like raisins imbedded in it.

Ernest Rutherford:
- Exposed a sheet of gold foil to a beam of alpha particles which are positively charged and noticed that not all of the alpha particles went straight through the foil; some of them rebounded or reflected off at different angles.
- Concluded that all atoms have a nucleus which holds positively charged particles.
- He later also discovered that the nucleus also has neutrally charged particles called neutrons.

Neils Bohr:
- Passed an electric current through hydrogen gas which made them glow.
- Concluded that the electrons around the nucleus must be in layers or shells, each of which has a different level of energy.