Chapter 7 Radioactivity

Question 1

What does an radioactive substance contain?

Answer 1

Unstable nuclei that becomes stable or less stable by emitting radiation

Question 2

What are the 3 main types of radiation?

Answer 2

Alpha, Beta, Gamma

Question 3

What do all stable nuclei have?

Answer 3

Neutrons and protons

Question 4

What is radioactive decay?

Answer 4

An unstable nucleus is described as decaying when it emits radiation. It is a random event.

Question 5

What do radioactive sources emit?

Answer 5

Alpha, beta or gamma radiation

Question 6

What is alpha radiation stopped by?

Answer 6

Paper

Question 7

What is beta radiation stopped by?

Answer 7

Aluminum

Question 8

What is gamma radiation stopped by?

Answer 8

Lead

Question 9

Which is the most penetrating type of radiation?

Answer 9

Gamma

Question 10

What happens in alpha decay?

Answer 10

The nucleus loses 2 protons and 2 neutrons

Question 11

What particles are emitted in alpha decay?

Answer 11

2 protons and 2 neutrons emitted as an alpha particle

Question 12

What is the alpha particle identical to?

Answer 12

A helium nucleus

Question 13

What is the atomic number?

Answer 13

The number of protons in the nucleus. Bottom number

Question 14

What is the mass number?

Answer 14

Number of protons plus neutrons in the nucleus. Top number

Question 15

What is an example of an alpha decay equation?

Answer 15

228. 224. +. 4
229. ——-> 88. Th. 2. a

You minus 4 from the mass number and 2 from the atomic number

Question 16

What is the relative mass and charge of a proton?

Answer 16

RM, 1
RC, +1

Question 17

What is the relative mass and charge of a neutron?

Answer 17

RM 1
RC 0

Question 18

What is the relative mass and charge of a electron?

Answer 18

RM 1/2000
RC -1

Question 19

What is an isotope?

Answer 19

Atoms of the same element with different numbers of neutrons. They have the same number of protons

Question 20

What is a beta particle?

Answer 20

An electron

Question 21

What is the relative mass and relative charge of a beta particle?

Answer 21

RM 0
RC -1

Question 22

What happens when an unstable nucleus emits a beta particle?

Answer 22

The atomic number of the nucleus goes up by one and its mass number is unchanged(neutron changes into a proton)

Question 23

What is an example of a beta decay question?

Answer 23

40 K ———> 40 Ca + 0B
19. 20. -1
1 is added to the atomic number

Question 24

Why are most nuclei stable?

Answer 24

Protons and neutrons are held together by a strong attractive force called strong nucleus force. This force is strong enough to overcome the electrostatic repulsion between protons and to stop neutrons moving away from the nucleus

Question 25

What happens in beta decay?

Answer 25

A neutron in the nucleus changes into a proton

Question 26

What particle is emitted in beta decay?

Answer 26

An electron is created in the nucleus and is immediately emitted

Question 27

What is gamma emission?

Answer 27

Electromagnetic radiation from a nucleus of an atom. Unchanged and has no mass. The emission does not change the number of protons or neutrons in a nucleus

Question 28

What is neutron emission?

Answer 28

Neutrons are emitted by some radioactive substances due to alpha particles colliding with the unstable nuclei in the substance. The collisions cause the unstable nuclei to become more unstable and emit a neutron. The emitted neutron has no charge they can pass through substances more easily than a or b particle can.

Question 29

What is alphas range in air?

Answer 29

5 cm

Question 30

What is betas range in air?

Answer 30

1m

Question 31

What is gammas range in air?

Answer 31

Unlimited it spreads out in air without being absorbed

Question 32

What has the greatest ionizing power?

Answer 32

Alpha because they have a large mass and high charge and they more quite slowly

Question 33

What is betas ionizing power?

Answer 33

Less than alpha and more than gamma

Question 34

What does ionization do to a living cell?

Answer 34

Damages or kills it

Question 36

What is the half life of a radioactive isotope?

Answer 36

The average time it takes for the number of nuclei of the isotopes in a sample to halve

Question 38

What is ionizing radiation?

Answer 38

Radiation that can knock electrons off atom’s creating positive ions

Question 39

What can radiation be measured with?

Answer 39

A geiger muller tube and counter records the count rate

Question 40

What is count rate?

Answer 40

Number of radiation counts per second

Question 41

What is activity measured in?

Answer 41

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

Question 42

What is irradiation?

Answer 42

Exposed to radiation

Question 43

What did John Dalton say?

Answer 43

Matter made up from tiny spheres that couldn’t be broken up. Different elements have different types of atoms

Question 44

What did JJ Thomson discover?

Answer 44

Electrons could be removed from atoms. Suggested plum pudding model(negative electrons stuck in positive atoms)

Question 45

What did Rutherford do?

Answer 45

Fired alpha particle at thin gold foil(alpha scattering). If the plum pudding model was correct they expected the particles to pass straight through or be slightly deflected. Most of the mass of the atom in the center in nucleus this also has positive charge. Some rebounded from foil

Question 46

What is Boris model of the atom?

Answer 46

Electrons in a atom orbit the nucleus at specific energy levels. Electrons in orbit can move to another orbit by absorbing electromagnetic radiation to move away or emitting electromagnetic radiation to move closer to the nucleus

Question 47

Experiment for penetrating power of radiation

Answer 47

-measure count rate without radioactive source present (background radiation) -measure count rate with source in place and subtract background radiation -test different materials -place each material between tube and radioactive source -add layers till count rate is 0 -to test range of radiation move the tube away from the source till count rate is 0 and measure distance