Radioactivity

Question 1

Which particles are found in the nucleus of the Atom?

Answer 1

Protons & Neutrons

Question 2

Which particle did Rutherford fire at gold leaf in his famous experiment?

Answer 2

Alpha particles

Question 3

What were the main observations and conclusions from Rutherford’s famous gold leaf experiment?

Answer 3

1) Most α go through = mostly empty space
2) Very few α deflected by large angles = dense central nucleus (very massive, very small)
3) Some α deflected by small amounts = nucleus has charge

Question 4

How big is an atom?

Answer 4

1 × 10 -10 m

(0.0000000001 metres)

Question 5

An isotope has the same number of ________ but a different number of ________.

Answer 5

An isotope has the same number of PROTONS but a different number of NEUTRONS.

Question 6

The mass number is:

Answer 6

Protons + neutrons

Question 7

Electrons exist in shells around the nucleus. Sometimes they jump up a level - how?

Answer 7

By absorbing just the right amount of energy to make the jump.

Question 8

Sometimes the electrons orbiting a nucleus absorb energy and jump up a level. When they drop back down what happens?

Answer 8

The emit electromagnetic radiation.

Question 9

What is ionisation?

Answer 9

When an electron gains enough energy to free itself from the nucleus, leaving an ion behind.

Question 10

What causes the majority of background radiation?

Answer 10

Radon gas

Question 11

Name the three main types of ionising radiation

Answer 11

Alpha
Beta (+/-)
Gamma

Question 12

What are the main properties of alpha radiation?

Answer 12

α
2 protons, 2 neutrons (He nucleus)
Charge: +2
Highly ionising
Range in air: few cm
Stopped by paper/skin

Question 13

What are the main properties of beta radiation?

Answer 13

β
High speed electron (-) or positron(+)
Charge: -1 (beta minus) +1 (beta plus)
Moderately ionising
Range in air: few metres
Stopped by aluminium

Question 14

What are the main properties of gamma radiation?

Answer 14

γ
Electromagnetic wave
No Charge, No mass
Weakly ionising
Range in air: few km - infinite
Stopped by lead or metres of concrete

Question 15

What happens to the mass and atomic number of a nucleus when it undergoes alpha decay?

Answer 15

Mass number goes down by 4
Atomic number goes down by 2

Question 16

What happens to the mass and atomic number of a nucleus when it undergoes beta minus decay?

Answer 16

Mass number remains the same
Atomic number increases by 1

Question 17

What happens to the mass and atomic number of a nucleus when it undergoes beta plus decay?

Answer 17

Mass number remains the same
Atomic number decreases by 1

Question 18

What happens to the mass and atomic number of a nucleus when it undergoes gamma decay?

Answer 18

No change to either Mass or Atomic number

Question 19

What happens to the mass and atomic number of a nucleus when it undergoes Neutron decay?

Answer 19

Mass number goes down by one
Atomic number remains the same

Question 20

Which type of radioactive decay involves a proton becoming a neutron?

Answer 20

A Proton becomes a neutron Plus a Positron in beta Plus decay

(Remember all the Ps!)

Question 21

Define half life

Answer 21

The average time taken for half of the radioactive nuclei in a sample of radioactive material to have decayed.

Question 22

What unit is activity measured in?

Answer 22

Becquerels (Bq)

Question 23

Describe two effects of ionising radiation on the human body.

Answer 23

1) Radiation burns/radiation sickness
2) Mutation of DNA within cells leading to cancer

Question 24

What is the difference between contamination and irradiation?

Answer 24

Irradiation: Only while you are in range of the source. Stops when you move away.

Contamination: You carry the source with you - (on clothes or ingested/inhaled) you continue to be irradiated.