3. The History of the Atom, Electronic Structure, Development of the Periodic Table and The Modern Periodic Table

John Dalton said atoms were what?

Solid spheres and said that different spheres made up different elements

What year did J.J. Thompson come up with the Plum Pudding model

1897

What did J.J. Thompson show his structure of the atom as?

The atom is a ball of positive charge with electrons stuck in it

How was Rutherfords model of the atom presented?

A tiny, positively charged nucleus at the centre where most of the mass is concentrated with a cloud of negative electrons surrounding it, so most of the atom is empty space

What is wrong with Rutherfords model?

If there was a ‘cloud’ of atoms surrounding the nucleus, the electrons would be attracted to the nucleus causing the atom to collapse

What was added to model of the atom by Niels Bohr?

Electrons were put in shells that are a fixed distance from the nucleus

What happened 20 years after the construction of the Niels-Bohr model?

James Chadwick discovered neutrons

Why do atoms react with other atoms?

To achieve a full outer shell

Until quite recently, how were elements arranged in the periodic table?

By their physical and chemical properties, and their atomic weight