Atomic structure

Question 1

What did Rutherford’s alpha scattering experiment prove?

Answer 1

1. Straight through particles = empty space in the atom
2. Slightly deflected = the alpha particles hit positively charged particles (protons)
3. Directly backwards = positive mass was concentrated in a tiny nucleus

Question 2

What was Niels Bohr’s discovery

Answer 2

Electrons orbit the nucleus at certain distances called energy levels

Question 3

What was James Chadwick’s discoveries

Answer 3

Neutrons to explain the imbalance between atomic and mass numbers

Question 4

Features of a proton

Answer 4

Mass = 1
Charge = +1

Question 5

Features of a neutron

Answer 5

Mass = 1
Charge = 0

Question 6

Features of an electron

Answer 6

Mass = 0
Charge = -1

Question 7

Why does an atom have no overall charge

Answer 7

Protons always equal electrons

Question 8

How can energy levels move in an atom

Answer 8

Absorbing or losing EM radiation

Question 9

What is an isotope

Answer 9

An atom with the regular number of protons (same charge) but different amount of neutrons (different mass)

Question 10

How many isotopes of an element are stable

Answer 10

1 or 2

Question 11

How do unstable isotopes attempt to become stable

Answer 11

Decay into other elements and give out radiation to try and become stable

Question 12

What is ionizing radiation

Answer 12

Radiation which knocks electrons off an atom, creatin an ion

Question 13

Features of an alpha particle

Answer 13

1. Helium nucleus (2 protons, 2 neutrons)
2. Not very penetrating (stopped by a few cm of air and absorbed by a sheet of paper)
3. Strongly ionizing

Question 14

Features of a beta particle

Answer 14

1. Fast moving electron
2. Moderately penetrating (can travel a few metres of air, absorbed by a sheet of aluminium)
3. For every beta particle emitted, a neutron becomes a proton

Question 15

Features of a gamma ray

Answer 15

1. Waves of electromagnetic radiation
2. Very penetrating (absorbed by thick sheets of lead/ concrete)
3. Weakly ionizing, as they pass straight through

Question 16

Nuclear equation for an alpha particle

Answer 16

1. • 4 from the mass
2. -2 from the atomic number
3. • a helium nucleus

Question 17

Nuclear equation for a beta particle

Answer 17

1. +1 to the atomic number
2. • a 0 weight, -1 atomic number electron

Question 18

How is radiation measured

Answer 18

Geiger Muller tube and counter

Question 19

What is half life

Answer 19

The time taken for the amount of radioactive nuclei in an isotope to halve

Question 20

What is radioactivity measured in

Answer 20

becquerels

Question 21

What does a short half life mean

Answer 21

1. Activity falls quickly
2. Nuclei are very unstable and decay quickly

Question 22

What does a long half life mean

Answer 22

1. Activity falls slowly
2. Most nuclei don’t decay for a long time

Question 23

How is half life shown on a graph

Answer 23

An exponential curve

Question 24

What is background radiation

Answer 24

Low level that is around us all the time due to the unstable isotopes in objects all around us

Question 25

Why do cosmic rays from the Sun not affect humans

Answer 25

The Earth's atmosphere block the radiation

Question 26

What does irradiated mean?

Answer 26

An object exposed to radiation

Question 26

3 sources of background radiation

Answer 26

1. Sun 2. Naturally occurring unstable isotopes 3. Human activity

Question 27

3 ways to avoid irradiation?

Answer 27

1. Lead lined boxes 2. Standing behind barriers 3. Remote controlled arms

Question 28

2 ways to avoid contamination?

Answer 28

1. Gloves 2. Tongs

Question 29

Which radiation types are most dangerous outside the body

Answer 29

Beta and gamma can penetrate skin and damage organs

Question 30

Which radiation type is most dangerous inside the body

Answer 30

Alpha ionize a very localised area

Question 31

Difference between irradiation and contamination

Answer 31

Irradiation is being exposed to a radioactive source, contamination is radiation getting inside or onto an object

Question 32

How can radiation damage the body?

Answer 32

Radiation can enter living cells and ionize atoms and molecules within them and cause mutant cells which divide uncontrollably (cancer)

Question 33

How are gamma rays used in medicine

Answer 33

1. Iodine 123 can detect if the thyroid is taking in iodine as it should 2. Gamma rays can be directed carefully at tumours to kill cancer cells without damaging normal cells

Question 34

Benefits of radiation treatment

Answer 34

1. Tracers can detect life threatening illnesses 2. Risk of cancer from one is very low 3. Cancer can be cleared

Question 35

Risks of radiation treatment

Answer 35

Side effects

Question 36

What is fission

Answer 36

Releasing energy from large, unstable nuclei by splitting them into smaller, lighter elements

Question 37

Explain fission

Answer 37

1. A nucleus absorbs a neutron 2. The nuclei split to form to similarly sized elements with some energy in their kinetic energy stores 2. Two or three nuclei are also released which, if moving slow enough, can be absorbed by another nuclei starting a chain reaction 4. Energy not in kinetic energy stores is released in gamma rays

Question 38

What can fission be used for

Answer 38

Remaining free neutrons and other decay products can heat water to make steam to turn turbines and generators

Question 38

How is fission controlled

Answer 38

Control rods in nuclear generators can be lowered and raised to absorb neutrons, slow down the reaction and control energy being released

Question 39

Explain fusion

Answer 39

1. Two light nuclei move towards each other at high speed to create a larger, heavier nucleus 2. The heavier nucleus does not have as much mass as the two lighter nuclei as some is converted into energy (gamma rays) 3, Lots of energy is released