2.1.1 The Changing Atom

Question 1

Why is the atom called ‘atom’?

Answer 1

Means ‘indivisible’

Question 2

What did Dalton’s atomic theory state?

Answer 2

All atoms of a given element are the same

Question 3

What proved atoms are not indivisible? What was this replaced with?

Answer 3

Cathode ray tubes emitted cathode rays (electrons), found
1. Were negative
2. Could be deflected by a magnet and magnetic field
3, Had negligible mass
- So replaced with plum-pudding, said overall charge of atom is +ive

Question 4

What disproved plum pudding?

Answer 4

Geiger and Marsden (Rutherford students) gold leaf experiment.

1. Expected: alpha particles passing thr plum budding atom undisturbed
2. Observed: a few deflected at sharp angles; by +ive nuc

Question 5

What was Bohr’s planetary model?

Answer 5

Said electrons orbited central nuc, or would spiral into its center. Came up with ‘shells’ and explained:

1. Spectral lines
2. Energy of e-‘s at diff distances from nuc

Question 6

What did Mosley do?

Answer 6

Found link between x-ray freq and el’s atomic no.

Question 7

Who discovered the proton?

Answer 7

Rutherford - explained Mosley’s findings: atomic no was linked to X-ray freqs

Question 8

What did de Broglie do?

Answer 8

1. Introduced the idea of atomic orbitals

2. Suggested that particles could have the nature of a wave and a particle

Question 9

What did James Chadwick do?

Answer 9

Discovered the neutron, by showing that some atoms emitted particles with the same mass as a proton - neutrons, as have no charge.