P2.5

Question 1

Where do radioactive substances emit radiation from

Answer 1

The nuclei of their atoms all the time

Question 2

What can new evidence cause

Answer 2

A theory to be re-evaluated

Question 3

What are most atoms

Answer 3

Empty space

Question 4

What is the basic structure of an atom

Answer 4

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

Question 5

Why does an atom have no overall charge

Answer 5

The number of protons = the number of electrons

Question 6

Where does some substances give out radiation

Answer 6

From the nuclei of their atoms all the time

Question 7

Origins of background radiation

Answer 7

Rocks
Cosmic rays from space
Nuclear weapons test
Nuclear accidents

Question 8

Nucleic structure of alpha particle

Answer 8

Same as helium
2 protons
2 neutrons

Question 9

What is gamma radiation

Answer 9

Type of electromagnetic radiation

Question 10

What is the difference between gamma with alpha and beta

Answer 10

Alpha and beta are deflected by both electric and magnetic fields

Question 11

What is the difference between beta and alpha

Answer 11

Alpha are deflected less than beta and in opposite direction

Question 12

Types of nuclear radiation

Answer 12

Beta
Alpha
Gamma

Question 13

What is a half life of a radioactive isotope

Answer 13

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

Question 14

Who came up with the nuclear model of the atom

Answer 14

Rutherford and Marsden

Question 15

Mass of an electron

Answer 15

1/2000

Question 16

Examples of isotopes

Answer 16

Carbon 12 and Carbon14

Question 17

How many stable isotopes of an element are there

Answer 17

One or two

Question 18

What does it mean that an isotope is unstable

Answer 18

They are radioactive so they decay and give off radiation

Question 19

What do radioactive substances spit out

Answer 19

One or more of alpha,beta and gamma radiation

Question 20

What is background radiation

Answer 20

Radiation that is present all the time

Question 21

Properties of alpha particles

Answer 21

Big
Heavy
Slow moving

Question 22

What does it mean that an alpha particle is strongly ionising

Answer 22

They bash into a lot of atoms and knock electrons off them before they slow down which creates lots of ions

Question 23

Why are alpha particles strongly ionising

Answer 23

They are big

Question 24

What are beta particles

Answer 24

Electrons

Question 25

Properties of a beta particle

Answer 25

``` Quite fast Quite small Penetrate moderately Long range in air Moderately ionising ```

Question 26

What happens when a beta particle is emitted

Answer 26

A neutron turns into a a proton.

Question 27

Why does a beta particle have a charge of -1 and a small mass

Answer 27

It is an electron

Question 28

Properties of a gamma ray

Answer 28

``` Penetrate far into materials without being stopped Pass straight through thin air Weakly ionising No mass No charge ```

Question 29

Why don't gamma rays get deflected by electric or magnetic fields

Answer 29

They are electromagnetic waves and have no charge

Question 30

The older a sample of a radioactive substance becomes

Answer 30

The less radiation it will emit

Question 31

Why do u have to use the idea of half life to measure how quickly the activity drops off

Answer 31

The activity never reaches zero

Question 32

What does a short half life mean

Answer 32

The activity falls quickly because lots of the nuclei decay quickly

Question 33

What does a long half life

Answer 33

The activity falls slowly because most of the nuclei don't decay for a long time