5. Atomic Physics

Question 1

Describe the nucleus of a radioactive atom

Answer 1

Most atoms each have a stable nucleus that doesn’t change
Atoms of a radioactive substance each have a nucleus that is unstable
They becomes stable by emitting alpha, beta or gamma radiation

Question 2

Describe alpha radiation

Answer 2

2 protons and 2 neutrons
Charge: +2
Mass: 4
Ionizing: strong
Penetration: not penetrating, stopped by paper

Question 3

Describe beta radiation

Answer 3

1 high energy electron
Charge: -1
Mass: 1/2000
Ionizing: moderate
Penetrating, stopped by aluminium

Question 4

Describe gamma radiation

Answer 4

It is electromagnetic wave -> electromagnetic radiation
Charge = 0
Mass = 0
Ionizing: weak
Very penetrating, only stopped by thick lead or concrete

Question 5

What is ionization

Answer 5

Radiation from radioactive substances knocks electrons out of atoms and the atoms become charged

Question 6

Describe alpha, beta and gamma deflection in electric fields

Answer 6

Gamma radiation is electrically neutral -> alpha and beta radiation can be deflected by the electric fields but gamma is not
Alpha particles are positively charged -> attract towards a negatively charged plate
Beta particles are negatively charged -> attract towards a positively charged plate

Question 7

Describe background radiation

Answer 7

Ionising radiation that is constantly present in our natural surroundings
Some come from natural sources: air, ground, cosmic
Some come from artificial sources: medical, food&drink, air travel, nuclear weapons

Question 8

Describe alpha, beta and gamma deflection in magnetic field

Answer 8

Beta radiation is easily deflected
Alpha radiation is deflected in the opposite direction to beta radiation bc they have opposite charges
Beta radiation is harder to deflect than alpha radiation bc it has much more mass -> more force to change its direction of motion
Gamma radiation is not deflected by a magnetic field

Question 9

Compare the ionization of alpha, beta and gamma radiation and suggest reason

Answer 9

Alpha > beta
Bc alpha particle has much more mass than beta particle and moves more slowly -> has much more effect on the atoms it encounters
Beta > Gamma
Bc beta particles are charged whereas gamma radiation is uncharged

Question 10

What is decay?

Answer 10

When an unstable nucleus emits radiation

Radioactive is a random event and cannot be predict or influence when it will happem

Question 11

Describe the decay of alpha, beta and gamma

Answer 11

Alpha radiation is released in the form of a helium atom
Beta is releases in the form of an electron
Gamma radiation: energy is released

Question 12

Define half life

Answer 12

The time taken for half the nuclei to decay

Question 13

What are some safety precaution when using radioactive substances

Answer 13

Wear protective clothing - gloves, lab coat, safety glasses
Radioactive stuff is stored in a lead container, in s locked cabinet
Picked up with tongs
Kept away from body, not pointed at ppl
Left out of its container for as short a time as possible

Question 14

Define isotope

Answer 14

Atoms of the same element with the same number of protons but with different number of neutrons