Atomic Structure

Question 1

What do atoms contain?

Answer 1

Positively charged nucleus made up of protons and neutrons, which is surrounded by negatively charged electrons

Question 2

What charge do protons have?

Answer 2

+1

Question 3

What charge do electrons have?

Answer 3

-1

Question 4

What overall charge does an atom have?

Answer 4

No charge as protons and electrons are equal

Question 5

When might the energy level of an electron change?

Answer 5

When the atom emits or absorbs electromagnetic radiation

Question 6

What does absorbing electromagnetic radiation do to an atom?

Answer 6

Moves electrons to a higher energy level, further from the nucleus

Question 7

When is electromagnetic radiation emitted?

Answer 7

When an electron drops to a lower energy level

Question 8

What does an atom that loses one of its outer electrons become?

Answer 8

A poitive ion

Question 9

What does an atom that gains an extra electron become?

Answer 9

A negative ion

Question 10

What is the number of protons in an element called?

Answer 10

Atomic number

Question 11

What is the total number protons and neutrons called?

Answer 11

The mass number

Question 12

What are atoms of the same element with a different number of neutrons called?

Answer 12

Isotopes

Question 13

Who discovered the electron?

Answer 13

J. J. Thompson

Question 14

When was the electron discovered

Answer 14

1897

Question 15

What did J. J. Thompsons discovery led to?

Answer 15

The plum pudding model

Question 16

What is the plum pudding model?

Answer 16

A positively charged solid sphere with negavtive electrons embedded throughout it

Question 17

What did Rutherford and Marsden do in 1905?

Answer 17

Bombarded thin gold foil with alpha particles

Question 18

What did the alpha scattering experiment prove?

Answer 18

That the plum pudding model was incorrect

Question 19

Why did the alpha scattering experiment prove that the plum pudding model was incorrect?

Answer 19

The heavy, positively charged alpha particles would have passed straight through it, but some of them were reflected back meaning they must have been repelled by the same charge the alpha particles carried

Question 20

What was the conclusion of the alpha scattering experiment?

Answer 20

The main mass of the atom was concentrated in the central nucleus which was positively charged
The electrons surrounded the nucleus

Question 21

What did Niels Bohr suggest?

Answer 21

That electrons orbit the nucleus at specific differences

Question 22

What did Chadwick prove the existence of?

Answer 22

The neutron

Question 23

What do some unstable atomic nuclei do?

Answer 23

Give out radiation to become stable

Question 24

What is the activity of a radioactive source?

Answer 24

The rate at which it decays

Question 25

What are the 3 main types of nuclear radiation?

Answer 25

Gamma, beta and alpha

Question 26

What is the ionising power of alpha radiation?

Answer 26

Strong ionising power

Question 27

What is the ionising power of beta radiation?

Answer 27

Reasonable power

Question 28

What is the ionising power of gamma radiation?

Answer 28

Poor ionising power

Question 29

What is alpha radiation absorbed by?

Answer 29

A few cm of air or a thin sheet of paper

Question 30

What is beta radiation absorbed by?

Answer 30

Absorbed by a few mm of aluminium

Question 31

What is gamma radiation absorbed by?

Answer 31

Many cm of lead or many m of concrete

Question 32

What are the components of alpha radiation?

Answer 32

Two neutrons and two protons ejected from the nucleus

Question 33

What are the hazards of alpha radiation?

Answer 33

Highly likely to be absorbed and cause damage if passed through living cells

Question 34

What are the components of beta radiation?

Answer 34

A high-speed electron ejected from the nucleus as a neutron turns into a proton

Question 35

What are the hazards of beta radiation?

Answer 35

Likely to cause damage if absorbed by living cells Can penetrate the body to inner organs

Question 36

What are the components of gamma radiation?

Answer 36

Electromagnetic radiation emitted from the nucleus

Question 37

What are the hazards of beta radiation?

Answer 37

Likely to pass through living cells without being absorbed and causing ionisation

Question 38

What is radioactive contamination?

Answer 38

THe unwanted presence of materials containing radioactive atoms or other material

Question 39

What is the hazard of radioactive contamination due to?

Answer 39

The decay of the contaminating atoms

Question 40

What is irradiation?

Answer 40

The process of exposing an object to nuclear radiation, it can be deliberate or accidental and does not cause the object to become radioactive

Question 41

What is half-life?

Answer 41

The average time it takes for half of the nuclei to decay The time it takes for the count rate, or activity of a sample containing the isotope to fall to 50% of its original value

Question 42

Describe an isotope with a short half-life.

Answer 42

Vary unstable and emit radiation very quickly, so exposure can be very hazardous Do not remain radioactive for long

Question 43

Describe an isotope with a long half-life.

Answer 43

They are more stable and remain radioactive for a very long time They emit radiation slowly, so exposure is less hazardous

Question 44

How is nuclear radiation involved in medical tracers?

Answer 44

A radioactive isotope is ingested or injected into the body As it travels around the body, it can be detected on the outside

Question 45

How can nuclear radiation be used to treat tumours?

Answer 45

A tumour in the thyroid gland could be treated with radioactive iodine, which gathers in the glands and destroys nearby cells A focussed beam of gamma rays can be used to destroy some tumours

Question 46

What is important to consider when choosing an isotope for a specific job?

Answer 46

Half-life, activity and type of radiation

Question 47

Why would a gamma source make the best tracer?

Answer 47

They can penetrate the body and be detected from outside They are the least ionising

Question 48

What do the levels of background radiation a person experiences depend on?

Answer 48

Location Job

Question 49

What is nuclear fission?

Answer 49

The splitting of an unstable nucleus (normally uranium or plutonium)

Question 50

What must usually happen for fission to occur?

Answer 50

The unstable nucleus must absorb a neutron first

Question 51

What happens during fission?

Answer 51

The nucleus splits into two nuclei of roughly equal size Emits two or three neutrons, gamma rays and energy

Question 52

What do all products of fission have?

Answer 52

Kinetic energy

Question 53

What can the neutrons emitted in nuclear fission begin?

Answer 53

A chain reaction

Question 54

Where is the reaction of nuclear fission controlled?

Answer 54

A nuclear reactor

Question 55

What is the explosion of a nuclear weapon caused by?

Answer 55

An uncontrolled chain reaction

Question 56

What can nuclear fusion be thought of as?

Answer 56

The opposite of nuclear fission

Question 57

What happens during nuclear fusion?

Answer 57

Two light nuclei join together to for a heavier nucleus Some of the mass is converted into energy and some of this energy is emitted as radiation

Question 58

What does nuclear fusion require?

Answer 58

A high temperature and pressure

Question 59

Why does nuclear fusion require high temperatures and pressure?

Answer 59

To overcome electrostatic forces Bring the positive nuclei close enough together so fusion can take place

Question 60

What happens when an alpha particle is emitted?

Answer 60

Mass number of an element is reduced by 4 Atomic number is reduced by 2

Question 61

What happens when beta decay occurs?

Answer 61

Mass number stays the same Atomic number increased by 1