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Physics > Atomic Structure And Radioactivity > Flashcards

Atomic Structure And Radioactivity Flashcards

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1
Q

What is the radius of an atom

A

1x10^-10 m

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2
Q

What particles are in the nucleus

A

Protons and neutrons

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3
Q

How can an electron move to a higher energy level

A

If an atom absorbs electromagnetic radiation an electron can move from a lower energy level to a higher energy level

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4
Q

Explain how an electron can move to a lower energy level

A

the atom can now emit electromagnetic radiation and the electron returns back to the lower energy level

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5
Q

What is the atomic number

A

The number of protons

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6
Q

Why do atoms have no overall charge

A

The number of electrons and protons are equal
So the negative charges on the electrons cancel out the positive charges on the protons

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7
Q

What is the mass number

A

The total number of neutrons and protons

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8
Q

What are isotopes

A

Atoms of the same element that have different numbers of neutrons

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9
Q

What ion is formed when an atom loses an electron

A

+

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10
Q

What ion is formed when an atom gains an electron

A

-

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11
Q

Describe the results of the alpha scattering experiment

A

Most of the alpha particles went straight through the gold foil, showing atoms are mainly empty space

Some alpha particles were deflected showing the centre of the atom has a positive charge

Few alpha particles bounced straight back showing the mass of the atom is concentrated in the nucleus

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12
Q

Which model replaced the plum pudding model due to the alpha scattering experiment

A

The nuclear model

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13
Q

Describe the nuclear model

A

The atom is mostly empty space
In the centre there is a positive nucleus
Around the edge there are electrons

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14
Q

Who developed the nuclear model

A

Ernest Rutherford

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15
Q

Explain how Niels Bohr adapted the nuclear model

A

By suggesting electrons orbit the nucleus at specific distances

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16
Q

Why was Bohr’s proposal accepted

A

It agreed with the results of experiments by other scientists

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17
Q

Who discovered neutrons

A

James Chadwick

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18
Q

Describe the order of discovery of protons neutrons and electrons

A

Electrons
Protons
Neutrons

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19
Q

Who discovered electron

A

JJ Thomson

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20
Q

What is radioactive decay

A

When an unstable nuclei gives out radiation to become stable
This is a random process

21
Q

What is activity

A

The rate at which a source of unstable nuclei decays

22
Q

What’s the unit for activity

A

Becqueral (Bq)

23
Q

What is the count rate

A

The number of decays recorded each second by a detector

24
Q

Describe an alpha particle

A

This consists of two neutrons and two protons, the same as a helium nucleus

25
Q

Describe a beta particle

A

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

26
Q

Describe a gamma ray

A

Electromagnetic radiation from the nucleus

27
Q

Other than alpha, beta, and gamma radiation what is another source of radiation

A

A neutron

28
Q

What are the properties of alpha particles

A

Short range in air, can travel a few cm before they collide with air particles and stop
Low penetrating power, they are stopped by a single sheet of paper
Very strongly ionising

29
Q

What are the properties of beta particles

A

Can travel few meters in air before stopping
Moderate penetrating power, stopped by a few millimeters of aluminum
Quite strongly ionising

30
Q

Properties of gamma radiation

A

High range in air, Travels several meters in air before stopping
High penetrating power, Stopped by several cm of lead
Weakly ionising

31
Q

Explain what happens to the mass number an atomic number during alpha decay

A

Mass number decreases by 4
Atomic number decreases by 2

32
Q

Explain what happens to the mass number and atomic number during beta decay

A

Mass number stays the same
Atomic number increases by 1

33
Q

What is the half-life

A

The time it takes for the number of nuclei of the isotope in a sample to halve, or the time it takes for the count rate from a sample containing the isotope to fall to half its initial level.

34
Q

What is radioactive contamination

A

The unwanted presence of materials containing radioactive atoms on other materials

35
Q

Explain why contamination is hazardous

A

Radioactive atoms decay and emit ionising radiation inside you

36
Q

What is irradiation

A

Exposing an object to nuclear radiation
The irradiated object does not become radioactive

37
Q

What is the risk of exposure to ionising radiation

A

Can increase the risk of cancer

38
Q

What are some precautions that can be taken for people who work with radioactive isotopes

A

Gloves can protect alpha radiation
Lead apron can be used for beta and gamma
Shielding

39
Q

Why should studies be published and shared with other scientists

A

This allows the findings to be checked by peer review

40
Q

What are the sources of background radiation

A

Natural:
Rocks
Cosmic rays from space

Man made:
Fallout from nuclear weapons testing
Nuclear accidents

41
Q

What are the uses of nuclear radiation in medicine

A

Exploration of internal organs
Control or destruction of unwanted tissue

42
Q

Problems with exploring internal organs using a tracer

A
  1. The tracer must emit radiation that can pass out of the body and be detected (gamma or beta radiation).
  2. The tracer must not be strongly ionising to minimise damage to body tissue.
  3. The tracer must not decay into another radioactive isotope.
  4. The tracer must have a short half-life so it is not present in the body for a long period.
43
Q

Problems with controlling or destroying unwanted tissue

A

Healthy tissue may also be destroyed as the radiation passes through the body

44
Q

What is nuclear fission

A

The splitting of a large and unstable nucleus

45
Q

Describe the process of nuclear fission

A

A larger unstable nucleus absorbs a neutron
The nucleus splits to form two smaller daughter nuclei
2 or 3 neutrons and gamma radiation is also emitted
Energy is released
All of the fission products have kinetic energy
Neutrons released can cause a chain reaction

46
Q

What is a controlled chain reaction used for

A

To release energy in a nuclear reactor

47
Q

What is the explosion In a nuclear weapon caused by

A

An uncontrolled fission chain reaction

48
Q

Describe the process of nuclear fusion

A

Two lighter nuclei join together to form a heavier nucleus
Some of the mass of the nuclei can be converted into energy, which is released as radiation

Physics (7 decks)

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