P6

Question 1

What are atomic nuclei composed of?

Answer 1

Atom nuclei are made up of protons and neutrons, and the nucleus of each element has a characteristic positive charge (unique)

Question 2

What are isotopes?

Answer 2

Isotopes are atoms of the same element that have different numbers of neutrons, thereby differing in nuclear mass, but not in charge

Question 3

What is the conventional representation of nuclei?

Answer 3

Nuclei are conventionally written in the format carbon-12, where the 12 refers to the number of subatomic particles inside the nucleus

Question 4

What can some nuclei be?

Answer 4

Some nuclei are unstable and may emit alpha particles, beta particles or neutrons, and electromagnetic waves as gamma rays

Question 5

What is the penetrating power for alpha?

Answer 5

Alpha has a weak penetrating power, which is absorbed by paper

Question 6

What is the penetrating power for beta?

Answer 6

Beta has a stronger penetrating power than alpha but weaker than gamma, being absorbed by aluminium

Question 7

What is the penetrating power for gamma?

Answer 7

Gamma has the strongest penetrating power, with most of it being stopped by a few cm of lead, although some may still go through

Question 8

What happens to the mass or charge of the nucleus when alpha radiation is emitted?

Answer 8

When an alpha particle is emitted, 2 protons and 2 neutrons leave the nucleus, so the mass goes down by 4 and the charge goes down by 2

Question 9

How do you write an equation for alpha decay?

Answer 9

Alpha decay equation: E1 —> E2 + He (nucleus, 4 2)

Both sides must add up

Question 10

What happens to the mass or charge of the nucleus when beta radiation is emitted?

Answer 10

A neutron decays into a proton and then an electron, which is then emitted from the nucleus, so the mass stays the same, but the charge on the nucleus increases by 1

Question 11

How do you write an equation for beta decay?

Answer 11

Beta decay equation: E1 —> E2 + 0, -1, e

Both sides must add up

Question 12

What happens to the mass or charge of the nucleus when gamma radiation is emitted?

Answer 12

When a nucleus emits a gamma ray, it isn’t affected as it is an electromagnetic wave, so it has no mass or charge

Question 13

What happens to the nucleus in neutron emission?

Answer 13

The charge doesn’t change, but the mass goes down by 1 as a neutron is emitted, making the element more stable

Question 14

How do you write an equation for neutron emission?

Answer 14

Neutron emission equation: E1 —> E2 + 1, 0 n

Both sides must add up

Question 15

Explain the concept of half life and how this is related to the random nature of radioactive decay

Answer 15

Half life is the time for the nuclei of half the atoms to decay. The probability that any nucleus decays in 1 second is fixed, which means that decay is random, as half life is constant

Question 16

What is the net decline?

Answer 16

The net decline is the ratio of the final activity to initial activity

Question 17

How do you calculate net decline after a given number of half-lives?

Answer 17

To calculate net decline, you work out the number of half lives and this is x
Then, express it as a ratio of 1:2^x

Question 18

How do you calculate half life?

Answer 18

number of half lives = activity / number of days per half life

Question 19

How are electrons arranged in comparison to the nucleus?

Answer 19

In each atom its electrons are arranged at different distances from the nucleus

Question 20

How may arrangements of an atom change in a nucleus?

Answer 20

Arrangements of an atom can change in a nucleus by the absorption or emission of EM radiation

Question 21

How can atoms become ions?

Answer 21

Atoms can become ions by the loss of electrons

Question 22

When can inner electrons be ‘excited’?

Answer 22

Inner electrons can be ‘excited’ when they absorb energy from radiation and rise to a higher energy level. When this energy is lost by the electron it is emitted as radiation.

Question 23

What is ionisation?

Answer 23

Ionisation is when outer electrons are lost from an atom

Question 24

What can changes in atoms and nuclei do?

Answer 24

Changes in atoms and nuclei can generate and absorb radiations over a wide frequency range, which is any part of the electromagnetic spectrum.

Question 25

What is contamination?

Answer 25

Contamination is having a radioactive material inside the body or on the skin. Once you are internally contaminated you cannot remove the radioactive material from inside you

Question 26

What is irradiation?

Answer 26

Irradiation is being exposed to radiation from an external source. The radiation can travel into your body but also out of it.

Question 27

Compare the hazards associated with contamination and irradiation

Answer 27

In both contamination and irradiation, ionising radiation can damage the DNA inside your cells, which can cause cancer.