P7 - Radioactivity

Question 1

Plum pudding model

Answer 1

JJ Thompson

Electrons were randomly distributed in a sphere of positive charge

Question 2

Alpha scattering experiment

Answer 2

Ernest Rutherford

Alpha particles were shot at gold foil with most going straight through or being deflected.

However, some came back proving that most of the mass was concentrated at the centre in a tiny nucleus

Also, they discovered that the nucleus must have a positive charge as it repelled the positive alpha particles at large angles

Question 3

Isotopes

Answer 3

Are atoms with the same number of protons but different number of neutrons

Question 4

Alpha particle

Answer 4

Contain two neutrons and two protons (helium atom)

Big, heavy, and slow-moving so therefore aren’t able to penetrate materials easily and stop quickly when traveling through the air

However, they are strongly ionising (when they collide with atoms to create ions)

Question 5

Beta particles

Answer 5

They are electrons

Move quite fast and are small

Penetrate moderately and have a long-range in the air with their ionising ability being moderate

Question 6

Gamma rays

Answer 6

They are very short-wavelength electromagnetic waves

Penetrate far into materials and pass straight through the air, therefore they are weakly ionising

They have no mass or charge

Question 7

Radioactive

Answer 7

A substance containing unstable nuclei that becomes stable by emitting radiations

Question 8

Background radiation

Answer 8

Radiation that is present at all times

E.g. food (bananas), x-rays, and cosmic rays from the Sun

Question 9

Half-life

Answer 9

The time taken for the number of radioactive nuclei to halve

Question 10

Carbon dating

Answer 10

Uses radioactive carbon to find the age of organic material