Atomic structure

Ideas about atoms have changed over time.

New evidence has been gathered from the experiments of scientists who have used their model of the atom to explain their observations and calculations.

Key ideas were proposed successively by Dalton, Thomson, Rutherford, and Bohr, before arriving at the model uused today.

Atoms that gain electrons form negative ions. If atoms lose electrons they form positive ions.

You can represent the atomic number and mass number of an atom using the notation 24/12Mg, where magnesiums atomic number is 12 and its mass number is 24.

Isotopes are atoms of the same element with different numbers of neutrons. They have identical chemical properties, but their physical properties, such as density can differ.