SP6 a-k

Question 1

What replaced the plum pudding model?

Answer 1

Rutherford’s nuclear model (gold foil experiment, fired alpha particles at thin gold sheet)

Question 2

What did the gold foil experiment show?

Answer 2

Most alpha particles passed through (atom mostly empty space), some deflected (positive nucleus)

Question 3

What are the relative masses of protons, neutrons, electrons?

Answer 3

Proton: 1, Neutron: 1, Electron: ~0 (1/1837)

Question 4

What is the atomic number?

Answer 4

Number of protons (also electrons if neutral)

Question 5

How do electrons move between energy levels?

Answer 5

Absorb energy → jump up; emit energy as light → fall down

Question 6

What is ionisation?

Answer 6

Electron removed completely (requires enough energy)

Question 7

What is β⁻ decay?

Answer 7

Neutron → proton + electron (ejected as β particle)

Question 8

Definition of half-life:

Answer 8

Time for half the radioactive nuclei to decay

Question 9

A sample decays from 200g to 25g in 60 years. What is its half-life?

Answer 9

200 → 100 → 50 → 25 (3 half-lives). 60 ÷ 3 = 20 years

Question 10

Medical uses of radiation:

Answer 10

Tracers (γ emitters like technetium-99).
Radiotherapy (γ rays kill cancer cells).

Question 11

Why is α dangerous if ingested?

Answer 11

High ionisation damages cells/DNA

Question 12

Describe alpha radiation

Answer 12

Helium nucleus, +2 charge, paper-stopped.
Most ionizing, least penetrating

Question 13

Describe beta radiation

Answer 13

High-speed electron, -1 charge, aluminum-stopped.
Moderate ionizing/penetrating, bends toward + plate.

Question 14

Describe gamma radiation

Answer 14

EM wave, no charge, lead-stopped.
Least ionizing, most penetrating.

Question 15

What is nuclear fission?

Answer 15

Splitting a heavy nucleus (e.g., uranium-235) into smaller nuclei + releases energy/neutrons