Topic P4

Question 1

What is the structure of the atom and how did it develop further

Answer 1

Tiny sphere that can’t be broken up

–> Electron discovery

Question 2

What is the structure of the plum pudding model and how did it develop further

Answer 2

Sphere of positive charge with negative electrons stuck in it

–> Alpha scattering experiment

Question 3

What is the structure of the Nuclear model and how did it develop further

Answer 3

Positively charged nucleus surrounded by cloud of negative electrons

–> Niels Bohr’s theoretical calculations agreed with experimental data

Question 4

What is the structure of the Bohr model1

Answer 4

Electrons orbit the nucleus at certain distances

Question 5

How did the Bohr model develop

Answer 5

It was found the nucleus could be split into smaller particles

1) The positive proton was found
2) 20 years later nuetrons were proved by James Chadwick

Question 6

What is the alpha particle experiment

Answer 6

Multiple alpha particles flew at a thin piece of gold foil and most passed through but a few deflected back

This showed:

• Most of the mass of the atom was concentrated at the centre (nuckeus)
• Nucleus is positively charged

Question 7

How do electrons move between energy levels

Answer 7

Electrons can absorb EM radiation to move to higher energy levels

or Electrons can emit EM radiation to move to lower energy levels

Question 8

What is the radius of the atom

Answer 8

radius = 1 x 10^-10 m

Question 9

What is an isotope

Answer 9

An isotope are atoms with the same number of protons but a different number of neutrons

Question 10

What is the mass number

Answer 10

The mass number is the top number

consists of the total number of protons and neutrons in an atom

Question 11

What is the atomic number

Answer 11

The atomic number is the bottom number and it has number of protons in the nucleus
number of protons = number of electrons
- shows the charge of the nucleus

Question 12

What is radioactive decay

Answer 12

When an unstable nucleus decays into another element and gives out radiation to become more stable

Question 13

What is ionising radiation

Answer 13

Radiation that knocks electrons off of atoms, creating positive ions

Question 14

what do unstable nuclei do

Answer 14

Unstable nuclei can also release neutrons when they decay

Question 15

What is in an alpha particle

Answer 15

2 neutrons
2 protons
- called a helium nucleus

Question 16

what are alpha particles absorbed by

Answer 16

sheet of paper

Question 17

alpha particle range in air

Answer 17

few cm

Question 18

how ionising is an alpha particle

Answer 18

very strong (most ionising)

Question 19

When are alpha particles used

Answer 19

In smoke detectors

Question 20

What is in a beta particle

Answer 20

fast moving electrons from nucleus

Question 21

What are beta particles absorbed by

Answer 21

Sheet of aliminuim

Question 22

beta particle range in air

Answer 22

few metres

Question 23

ioising power of beta particle

Answer 23

Moderately powerful

Question 24

When are beta particles used

Answer 24

Material thickness testing

Question 25

What is gamma particles made of

Answer 25

electromagnetic radiation from nucleus

Question 26

gamma particles absorbed by

Answer 26

Thick sheets of lead

Question 27

gamma particle range in air

Answer 27

Longer distances

Question 28

gamma particles ionising power

Answer 28

weak - least ionising

Question 29

Gamma particle exmaple of use

Answer 29

Medical tracers

Question 30

What happens to the atomic and mass number during alpha decay

Answer 30

mass number decreases

atomic number decreases

Question 31

What happens to the atomic and mass number during beta decay

Answer 31

mass number stays the same

atomic number increases

Question 32

What happens to the atomic and mass number during gamma decay

Answer 32

Mass number and atomic number stay the same

Question 33

What does activity mean

Answer 33

The rate at which a source decays

measured in becquerels (bq)

Question 34

What does count rate mean

Answer 34

The number of radiation counts reaching a detector per second

Question 35

What measures count rate

Answer 35

A Geiger-Muller tube and counter

Question 36

What is radioactive contamination

Answer 36

Getting unwanted radioactive atoms onto or into an object

Question 37

What does irradiation mean

Answer 37

The exposure of an object to nuclear radiation (doesn’t make the object radioactive)

Question 38

What are 3 precautions to protect against irradtiation

Answer 38

1) Keep sources in lead-lined boxes
2) Stand behind barriers or be in a different room to the source
3) Handle sources with remote controlled arms

Question 39

Is radioactive decay random - TRUE/FALSE

Answer 39

TRUE

Question 40

What is a half life

Answer 40

Time taken for the number of nuclei of an isotope in a sample to halve

Question 41

How to work out half life on graph

Answer 41

look at video

Question 42

Which are the most dangerous radiation particles to get in your body

Answer 42

most = alpha particle 
least = gamma particle

Question 43

What is the most dangerouse radioactive particle to get outside your body

Answer 43

Most = gamma 
least = alpha

Question 44

What is the risk of radiation

Answer 44

1) radiation can enter a living cell, ionising atoms within it
2) cells can be damaged and can multiply and become cancer
or
2) Cells can be killed