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Physics > Atomic Structure > Flashcards

Atomic Structure Flashcards

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1
Q

What do atoms contain?

A

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

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2
Q

What charge do protons have?

A

+1

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3
Q

What charge do electrons have?

A

-1

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4
Q

What overall charge does an atom have?

A

No charge as protons and electrons are equal

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5
Q

When might the energy level of an electron change?

A

When the atom emits or absorbs electromagnetic radiation

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6
Q

What does absorbing electromagnetic radiation do to an atom?

A

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

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7
Q

When is electromagnetic radiation emitted?

A

When an electron drops to a lower energy level

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8
Q

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

A

A poitive ion

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9
Q

What does an atom that gains an extra electron become?

A

A negative ion

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10
Q

What is the number of protons in an element called?

A

Atomic number

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11
Q

What is the total number protons and neutrons called?

A

The mass number

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12
Q

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

A

Isotopes

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13
Q

Who discovered the electron?

A

J. J. Thompson

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14
Q

When was the electron discovered

A

1897

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15
Q

What did J. J. Thompsons discovery led to?

A

The plum pudding model

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16
Q

What is the plum pudding model?

A

A positively charged solid sphere with negavtive electrons embedded throughout it

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17
Q

What did Rutherford and Marsden do in 1905?

A

Bombarded thin gold foil with alpha particles

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18
Q

What did the alpha scattering experiment prove?

A

That the plum pudding model was incorrect

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19
Q

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

A

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

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20
Q

What was the conclusion of the alpha scattering experiment?

A

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

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21
Q

What did Niels Bohr suggest?

A

That electrons orbit the nucleus at specific differences

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22
Q

What did Chadwick prove the existence of?

A

The neutron

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23
Q

What do some unstable atomic nuclei do?

A

Give out radiation to become stable

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24
Q

What is the activity of a radioactive source?

A

The rate at which it decays

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25
Q

What are the 3 main types of nuclear radiation?

A

Gamma, beta and alpha

26
Q

What is the ionising power of alpha radiation?

A

Strong ionising power

27
Q

What is the ionising power of beta radiation?

A

Reasonable power

28
Q

What is the ionising power of gamma radiation?

A

Poor ionising power

29
Q

What is alpha radiation absorbed by?

A

A few cm of air or a thin sheet of paper

30
Q

What is beta radiation absorbed by?

A

Absorbed by a few mm of aluminium

31
Q

What is gamma radiation absorbed by?

A

Many cm of lead or many m of concrete

32
Q

What are the components of alpha radiation?

A

Two neutrons and two protons ejected from the nucleus

33
Q

What are the hazards of alpha radiation?

A

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

34
Q

What are the components of beta radiation?

A

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

35
Q

What are the hazards of beta radiation?

A

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

36
Q

What are the components of gamma radiation?

A

Electromagnetic radiation emitted from the nucleus

37
Q

What are the hazards of beta radiation?

A

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

38
Q

What is radioactive contamination?

A

THe unwanted presence of materials containing radioactive atoms or other material

39
Q

What is the hazard of radioactive contamination due to?

A

The decay of the contaminating atoms

40
Q

What is irradiation?

A

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

41
Q

What is half-life?

A

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

42
Q

Describe an isotope with a short half-life.

A

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

43
Q

Describe an isotope with a long half-life.

A

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

44
Q

How is nuclear radiation involved in medical tracers?

A

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

45
Q

How can nuclear radiation be used to treat tumours?

A

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

46
Q

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

A

Half-life, activity and type of radiation

47
Q

Why would a gamma source make the best tracer?

A

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

48
Q

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

A

Location
Job

49
Q

What is nuclear fission?

A

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

50
Q

What must usually happen for fission to occur?

A

The unstable nucleus must absorb a neutron first

51
Q

What happens during fission?

A

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

52
Q

What do all products of fission have?

A

Kinetic energy

53
Q

What can the neutrons emitted in nuclear fission begin?

A

A chain reaction

54
Q

Where is the reaction of nuclear fission controlled?

A

A nuclear reactor

55
Q

What is the explosion of a nuclear weapon caused by?

A

An uncontrolled chain reaction

56
Q

What can nuclear fusion be thought of as?

A

The opposite of nuclear fission

57
Q

What happens during nuclear fusion?

A

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

58
Q

What does nuclear fusion require?

A

A high temperature and pressure

59
Q

Why does nuclear fusion require high temperatures and pressure?

A

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

60
Q

What happens when an alpha particle is emitted?

A

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

61
Q

What happens when beta decay occurs?

A

Mass number stays the same
Atomic number increased by 1

Physics (8 decks)

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