Atom Models

Question 1

Who created the plum pudding model? (And when)

Answer 1

JJ Thomson
1890

Question 2

What was the plum pudding model? (1890)

Answer 2

Sea of positive charge with dense, placed electrons

Question 3

What was the Rutherford (Geiger and Marsden’s) model? (1909)

Answer 3

Small, dense positively charged nucleus surrounded by orbiting electrons

Question 4

Describe Rutherfords gold foil experiment (1909)

Answer 4

An alpha particle source emits the alpha beam, then goes in different directions when aimed at the gold leaf. The particles scatter and can be seen using the detector screen and movable microscope and can then be recorded.

Question 5

How do the alpha particles behave when aimed at a nucleus?

Answer 5

A few (1 in 8000) bounce back, deflected by >90*. (Because the nucleus is small)
Some are deflected by the positive charge in the nucleus.
Most alpha particles go straight through (because it’s mostly empty space).

Question 6

What is an excited electron

Answer 6

If an electron in an atom has energy transferred to it then the electron can become excited and increase its energy level (may move to another electron shell or become ionised)

Question 7

What was Democritus’ theory?

Answer 7

Invisible atoma 3000BC

Question 8

What’s John daltons theory? (1803)

Answer 8

Atoms as solid spheres

Question 9

What was Bohr’s theory? (1913)

Answer 9

Electron shells

Question 10

What was James Chadwicke’s theory? (1932)

Answer 10

Neutron