Combined Physics - P4 Atomic Structure

Question 1

Approximately how big is the radius of an atom?

Answer 1

Very small – a radius of about 1x10^-10 m

Question 2

How much smaller is the radius of a nucleus compared with the radius of an atom?

Answer 2

The radius of the nucleus is approximately 1/10,000^th the radius of an atom

Question 3

What happens when electrons fall to a lower energy level (closer to the nucleus)?

Answer 3

They release electromagnetic radiation

Question 4

What does contamination mean in terms of radioactivity?

Answer 4

If a substance is contaminated, it’s covered in radioactive material.

Question 5

What two subatomic particles are in the nucleus of an atom?

Answer 5

Protons and Neutrons

Question 6

What happens if the electrons in an atom absorb electromagnetic radiation?

Answer 6

They move to a higher energy level (further from the nucleus).

Question 7

What is the overall electrical charge of an atom?

Answer 7

No overall charge – electron and proton numbers are equal

Question 8

What does irradiation mean?

Answer 8

Exposing an object to nuclear radiation (the object itself does not become radioactive)

Question 9

What is the mass number of an atom?

Answer 9

The number of protons and neutrons in an atom

Question 10

What is an isotope?

Answer 10

Atoms of the same element with different numbers of neutrons.

Question 11

Before the discovery of the electron, what were atoms thought to be (as suggested by Dalton)?

Answer 11

Tiny spheres that could not be divided

Question 12

What did Rutherford’s scattering experiment reveal about the atom?

Answer 12

• The mass of the atom was concentrated in the centre (nucleus).
• The nucleus was small.
• The nucleus was positively charged.

Question 13

What precautions should be taken around hazardous radioactive materials?

Answer 13

• Wearing gloves / using tongs
• Protective suits
• Breathing apparatus
• Limiting exposure time

Question 14

What happens to an atom if it loses one or more outer electron(s)?

Answer 14

It becomes a positive ion.

Question 15

What was the Plum Pudding model?

Answer 15

The atom was suggested to be a ball of positive charge with negative electrons embedded in it.

Question 16

How did Bohr adapt the nuclear model of the atom?

Answer 16

Bohr suggested electrons orbit the nucleus at specific distances (energy levels).

Question 17

List alpha, beta and gamma radiation from most to least ionising.

Answer 17

Alpha (most ionising)

Beta (moderately ionising)

Gamma (least ionising)

Question 18

Name the three types of radiation that can be emitted by unstable nuclei.

Answer 18

• Alpha radiation
• Beta radiation
• Gamma radiation

Question 19

What is nuclear ‘activity’ measured in?

Answer 19

Becquerels (Bq) where 1 Bq is 1 decay per second

Question 20

List alpha, beta and gamma radiation in terms of their range in air (from shortest to longest).

Answer 20

Alpha (shortest range in air, few cm)

Beta (moderate range in air, few m)

Gamma (longest range in air)

Question 21

What sub-atomic particle was discovered by James Chadwick?

Answer 21

Neutron

Question 22

List alpha, beta and gamma radiation from most penetrating to least penetrating.

Answer 22

Gamma (most penetrating)

Beta (moderately penetrating)

Alpha (least penetrating)

Question 23

Name the equipment used to measure radioactivity.

Answer 23

Geiger-Muller Tube

Question 24

What is alpha (α) radiation?

Answer 24

A helium nucleus (2 neutrons and 2 protons)

Question 25

What is beta radiation?

Answer 25

A fast-moving electron

Question 26

What is gamma radiation?

Answer 26

An electromagnetic wave

Question 27

As well as alpha, beta and gamma radiation what else can radiative substances release from their nuclei?

Answer 27

neutrons

Question 28

How is an alpha particle represented in a nuclear equation?

Answer 28

Question 29

Inside the body what radioactive source is most dangerous?

Answer 29

Alpha

Question 30

Name the material that stops:

a) Alpha radiation
b) Beta radiation
c) Gamma radiation

Answer 30

a) Paper stops alpha radiation
b) A fem mm of aluminium stops beta radiation
c) Thick sheets of lead or metres of concrete stops gamma radiation

Question 31

How is a beta particle represented in a nuclear equation?

Answer 31

Question 32

Complete the nuclear equation for the alpha decay of Radon²¹⁹.

Answer 32

Question 33

Complete the nuclear equation for the beta decay of Carbon-14.

Answer 33

Question 34

What happens to the mass or charge of a nucleus when it experiences gamma emission?

Answer 34

The mass and charge remain the same

Question 35

What happens to the radioactivity of a source over time?

Answer 35

It decreases

Question 36

What is the half-life of the following sample?

Answer 36

2 days

Question 37

Outside of the body what radioactive sources are most dangerous?

Answer 37

Beta and Gamma

Question 38

How can the process of radioactivity be described?

Answer 38

Random

Question 39

What is half-life?

Answer 39

The time taken for the number of nuclei of a radioactive isotope to halve (or the count rate to halve)

Question 40

Higher Q. How can net decline in radioactivity be calculated?

Answer 40

1. Find the activity after each half-life
2. Divide the final activity by the initial
3. Multiply by 100 to make a percentage