Physics topic 4

Question 1

what is an alpha particle

Answer 1

two protons and two neutrons

Question 2

what is a beta particle

Answer 2

fast moving electrons released due to neutron changing into a proton

Question 3

what is a gamma ray

Answer 3

electromagnetic radiation released by the nucleus.

Question 4

alpha radiation is used in

Answer 4

smoke alarms by
- ionising air particles, causing current to flow.
- if there is smoke around, it binds to the ionised air and causes the current to stop, setting off the alarm.

Question 5

beta radiation can be used to

Answer 5

• test thickness of metal sheets
• as beta particles would penetrate further than alpha particles, but would not penetrate as far as gamma rays.

Question 6

neutrons can also be released

Answer 6

• when atoms decay, to rebalance their atomic and mass numbers

Question 7

alpha particle characteristics

Answer 7

• strongly ionising
• range of few cm in air
• stopped by sheet of paper

Question 8

beta particle characteristics

Answer 8

• moderately ionising
• range of few m in air
• stopped by sheet of aluminium

Question 9

gamma ray characteristics

Answer 9

• weakly ionising
• long range of distance in air
• stopped by thick sheets of lead or metres of concrete.

Question 10

ionising radiation is..

Answer 10

radiation that knocks electrons off atoms, creating positive ions. How ionising a radiation source is is how easily it does this.

Question 11

order of people in atom development x5

Answer 11

• John dalton
• JJ Thompson
• Rutherford
• Bohr
• Chadwick

Question 12

Daltons model

Answer 12

• atom made up of tiny spheres that couldn’t be broken up
• each element made up of a different type of atom

Question 13

JJ Thompson model

Answer 13

-discovered electrons that could be removed from atoms
- plum pudding model - positive ball of mass with negative electrons embedded.

Question 14

Rutherford model

Answer 14

• alpha scattering experiment
• expected particles to pass through
• ones at mass deflected
• few deflected at large angles
• most passed straight through
• so most of atom is empty
• nucleus is positively charged
• most of mass concentrated at tiny nucleus in the middle of the atom

Question 15

Niels Bohr model

Answer 15

• different nuclear model
• said atoms orbit nucleus at certain distances called energy levels
• discovered protons which has a positive charge

Question 16

James Chadwick

Answer 16

• proved the existence of neutron.

Question 17

electrons can move between energy levels by

Answer 17

• absorbing or releasing electromagnetic radiation
• if electron in valence shell absorbs em rad then it can leave the atom

Question 18

the total atomic and mass numbers on both sides of the arrow must be

Answer 18

equal

Question 19

beta decay

Answer 19

increases the charge of the nucleus
- protons increase by 1 and neutrons decrease by 1.
- so charge increases by 1 but mass stays the same.

0
-1 e

Question 20

alpha decay

Answer 20

decreases the charge and mass of the nucleus
- when nucleus emits alpha particle it loses 2 protons and 2 neutrons.
- so atomic number decreases by 2 and mass number decreases by 4
- charge of nucleus decreases

4
2

Question 21

gamma rays

Answer 21

don’t change mass or charge of nucleus
- gamma rays are way of getting rid of excess energy from a nucleus
- so there is no change to the mass number or atomic number of the atom.