P4: Atomic Structure & Radioactivity

Question 1

What are electrons?

Answer 1

Negatively charged particles that orbit the nucleus of an atom in outer shells.

Question 2

What are protons?

Answer 2

Positively charged particles in the middle of the nucleus of an atom.

Question 3

What are neutrons?

Answer 3

Particles with no charge that are in the middle of the nucleus of an atom

Question 4

What is a radioactive half-life?

Answer 4

The amount of time it takes for the nuclei to split

Question 5

Alpha decay(5):

Answer 5

It is very easily stopped(even by a piece of paper)
Strongly effected by a magnetic field
It is the most charged and ionising particle
Heaviest particle
When an atom looses an alpha particle the atomic no.= -2
mass no. = -4

Question 6

Beta radiation(4):

Answer 6

Much lighter than an alpha particle
Can be stopped by 5mm of aluminium
Negative charge
When an atom looses a beta particle the atomic no. =+1

Question 7

Gamma radiation(4)

Answer 7

It is a wave
Can go through aluminium but is stopped by lead
It is the most penetrative 
No charge or mass
It is hard to stop

Question 8

Describe the difference between contamination and irradiation

Answer 8

Irradiation is to expose an object to nuclear radiation whereas contamination is the unwanted presence of materials containing radioactive atoms

Question 9

What is nuclear fission?

Answer 9

The splitting of an atomic nucleus into parts.

Question 10

What is nuclear fusion?

Answer 10

A reaction in which two light nuclei combine to form a

heavier nucleus with the release of energy

Question 11

What plum pudding model?

Answer 11

The plum pudding model, by JJ Thompson, is a ball of positive charge with negative electrons spread across it.

Question 12

Why did they change the plum pudding model?(2)

Answer 12

Geiger and Mardsen carried out this experiment where they shot alpha particles at a gold foil. This disproved the plum pudding model as some of the particles bounce of the foil , meaning the atom had a nucleus

Question 13

Isotope(definition):

Answer 13

Atoms of the same of the same element with a different number of neutrons in the nucleus

Question 14

Irradiation(definition):

Answer 14

To expose an object to nuclear radiation

Question 15

Ionizing(definition):

Answer 15

Refers to radiation that can cause atoms to loose or gain electrons, becoming ions

Question 16

How do smoke alarms use radiation?(3)

Answer 16

• Alpha particles from the alarm ionize air molecules.
• This allows positive and negative ions to constantly flow through the smoke alarm
• In case of fire the smoke alarm will be triggered by the smoke because it disturbs the flow of ions

Question 17

How do X-rays use radiation?(2)

Answer 17

• The gamma radiation passes through the body

- A detector on the other side pics up the radiation and creates an image

Question 18

How is radiation used to control the thickness of metal?

Answer 18

The amount of radiation which passes through a material can

be detected and used to control the thickness of the material.

Question 19

Nuclear fission:

Answer 19

The splitting of an atomic nucleus into parts, either spontaneously or as a result of the impact of a particle usually with an associated release of energy

Question 20

Nuclear fusion:

Answer 20

A reaction in which two nuclei combine to form a heavy nucleus with the release of energy

Question 21

Radiation{definition}(2):

Answer 21

A type of energy that is released from the nucleus of atoms. It is the process by which atoms become stable

Question 22

If the ratio between protons and neutrons is unstable…

Answer 22

the atom becomes unstable

Question 23

Neutron radiation(definition)(2):

Answer 23

The release of a high speed neutron from the nucleus. can also be the result of nuclear fission.

Question 24

Radioisotope(definition):

Answer 24

An atom with an unstable nucleus

Question 25

Why is radioactivity difficult to measure?

Answer 25

Radioactivity is random and cannot be affected by physical changes

Question 26

The radius of an atom is approximately…

Answer 26

1 x10^-10

Question 27

Why is radiation dangerous?

Answer 27

Radiation can affect the way in which our cells work and cause them to mutate leading to cancers

Question 28

Nuclear fission process (3):

Answer 28

• The unstable nucleus absorbs a neutron
• The nucleus splits into 2 smaller nuclei and emits 2 or 3 neutrons plus gamma rays
• Energy is released by the fission reaction

Question 29

Background radiation(2):

Answer 29

• comes from natural sources such as rock and cosmic rays from space
• or it comes from man-made sources such as fallout from nuclear weapons and nuclear accidents