Radioactive decay

Question 1

What is the basic structure of an atom?

Answer 1

A small central nucleus composed of protons and neutrons surrounded by electrons.

Question 2

What is the relative mass of a neutron?

Answer 2

1.

Question 3

What is the relative mass of a proton?

Answer 3

1.

Question 4

What is the relative mass of an electron?

Answer 4

Very small (1/2000).

Question 5

What is the relative charge of a neutron?

Answer 5

0.

Question 6

What is the relative charge of a proton?

Answer 6

+1.

Question 7

What is the relative charge of an electron?

Answer 7

-1.

Question 8

In an atom the number of electrons is equal to…

Answer 8

…the number of protons in the nucleus.

Question 9

What can be said about the overall electrical charge in and atom?

Answer 9

There is no overall charge because the number of protons is equal to the number of electrons.

Question 10

When an atom gains or loses electrons it becomes a what?

Answer 10

An ion.

Question 11

Atoms of an element always have the same number of protons, but what is an atom of an element if it has a different number of neutrons?

Answer 11

An isotope of that element.

Question 12

The total number of protons in an atom is known as what?

Answer 12

The atomic number.

Question 13

The total number of protons and neutrons in an atom is known as what?

Answer 13

The mass number.

Question 14

A substance is referred to as radioactive if it does what?

Answer 14

Gives out radiation all the time from the nuclei of its atoms no matter what is done to it.

Question 15

True or false, radioactive decay is systematic?

Answer 15

False, radioactive decay is a random process.

Question 16

What are the origins of background radiation?

Answer 16

The rocks we live above.
Radiation from space.
Building materials.
Nuclear accidents.
Nuclear weapons testing.

Question 17

What is an alpha particle?

Answer 17

A particle with only two neutrons and two protons (the same as a helium nucleus).

Question 18

What is a beta particle?

Answer 18

An electron from the nucleus.

Question 19

What is gamma radiation?

Answer 19

Electromagnetic radiation in the form of gamma rays.

Question 20

Properties of alpha particles?

Answer 20

1/3 speed of light, weakly effected by magnetic field, strongly ionising, +2 charge, travels short distance in air and won’t penetrate skin/paper.

Question 21

Properties of beta particles?

Answer 21

2/3 speed of light, strongly effected by magnetic field, weakly ionising, -1 charge, penetrates skin/paper but absorbed by aluminium.

Question 22

Properties of gamma rays?

Answer 22

Speed of light, no magnetic effect, very weakly ionising, 0 charge or mass, stopped by thick lead or concrete.

Question 23

What is meant by the term ionising?

Answer 23

The radiation can break molecules into ions.

Question 24

What types of radiation can be deflected by a magnetic field?

Answer 24

Alpha and beta radiation can be deflected, however a magnetic field has no effect on gamma radiation.

Question 25

Alpha radiation can be used how?

Answer 25

Used in smoke alarms. When smoke moves between the source and detector the radiation is absorbed and the alarm sounds.

Question 26

How can beta radiation be used?

Answer 26

In paper mills. If the paper is thicker between the source and detector more radiation is absorbed so the rollers are narrowed and the paper is made thinner. If the paper is thin less radiation is absorbed so the rollers are widened to make the paper thicker.

Question 27

Uses of gamma radiation?

Answer 27

Sterilisation of food and medical equipment.
Radiotherapy.
Leaking pipes (put source in pipe with short half life and detect where the leak is).

Question 28

What is the half life of a radioactive isotope?

Answer 28

The average length of time it takes for the number of nuclei of an isotope in a sample to half, or the time it takes for the count rate of a sample containing the isotope to fall to half its initial level.