Atomic theory

Question 1

John Dalton

Answer 1

proposed atomic theory:
1. Elements consist of very small particles called atoms
2. all atoms of a given element are identical and have the same size, mass, and chemical properties and these are different to other elements
3. atoms are not created or destroyed during chemical reactions
4. compounds form when elements combine in specific ratios

Question 2

J.J Thomson

Answer 2

experimented with cathode ray tubes which showed that all atoms contain tiny negatively charged subatomic particles.

negative particles that existed were spread through the positively charged sphere of the atom like raisins in a pudding.

Plum Pudding

Question 3

Ernest Rutherford

Answer 3

• Ernest Rutherford fired beams of alpha particles (charged helium nuclei) at a sample of gold foil.
• a small number were deflected or even deflected back toward the alpha source.
• implied that most of an atom is empty space to allow most alpha particle to remain unaffected and most of the mass is in a tiny space which results in the deflections

Question 4

Sir James Chadwick

Answer 4

• neutron was confirmed by Rutherford’s student James Chadwick.
• achieved by studying the emissions of Beryllium by alpha particle bombardment: