Chemistry - atomic structure and the periodic table

Who invented the fist atomic model?

John Dalton

What is Dalton’s model about?

Atoms were believed to be tiny spheres that could not be divded

Who discovered the Plum Pudding Model?

JJ Thompson

What did Thompson discover?

He discovered the electron and proposed that atoms were balls of positive charge with embedded negative electrons.

Who discovered the nuclear model?

Ernest Rutherford

What did Rutherford discover?

He conducted the alpha scattering experiment and found that the mass of the atom was concentrated at its centre in a positively charged nucleus.

• most particles pass through so the atom is mostly empty space

• a small number of alpha particles being deflected suggested that there is a concentration of positive charge in the atom

• the very small number of alpha particles coming straight back suggested that the positive charge and mass are concentrated in a tiny nucleus

What did Bohr discover?

Electrons orbit the nucleus in shells and in fixed distances

Who discovered protons?

Rutherford

Timeline of subatomic particle discovery

Electrons, protons, neutrons

Who discovered the neutrons?

James Chadwick

Radius of an atom

1 × 10^-10 m

Radius of a nucleus

1 × 10^-14 m

Who invented the modern periodic table?

Dmitri Mendeleev

What did Mendeleev do to the periodic table?

Elements are ordered according to their atomic weights. Later it is ordered according to atomic weight instead.