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Physics > 4. Atomic Structure > Flashcards

4. Atomic Structure Flashcards

1
Q

What is the approximation for the radius of an atom?

A

1x10⁻¹⁰ metres.

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2
Q

What are the three subatomic constituents of an atom?

A
  1. Proton 2. Neutron 3. Electron
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3
Q

Where is most of the mass of an atom concentrated?

A

In the nucleus.

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4
Q

What proportion of the total radius of an atom is the radius of the nucleus?

A

1/10000th

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5
Q

Describe the arrangement of protons

A

neutrons

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6
Q

What charge does the nucleus of an atom have? Why?

A
  • Positive charge. - The nucleus contains protons (positive charge) and neutrons (no charge).
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7
Q

Give two ways that an atom’s electron arrangement can be changed.

A
  1. Absorbing electromagnetic radiation. 2. Emitting electromagnetic radiation.
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8
Q

How does an atom’s electron arrangement change when it absorbs EM radiation?

A

Electrons move further away from the nucleus (higher energy level).

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9
Q

How does an atom’s electron arrangement change when it emits EM radiation?

A

Electrons move closer to the nucleus (lower energy level).

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10
Q

How does the ratio of electrons to protons result in the atom having no overall charge?

A

The number of protons equals the number of electrons, and their charges cancel each other out.

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11
Q

What do all forms of the same element have in common?

A

They all have the same number of protons.

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12
Q

What is the atomic number?

A

The number of protons in an atom.

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13
Q

What is an atom’s mass number?

A

The total number of protons and neutrons in the atom.

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14
Q

What is an isotope?

A

An atom of an element that has a different number of neutrons but the same number of protons.

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15
Q

How do atoms turn into positive ions?

A

By losing one or more electrons.

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16
Q

What may lead to a scientific model being changed or replaced?

A

Discovery of new experimental evidence that doesn’t agree with the existing theory.

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17
Q

How did the plum-pudding model describe the atom?

A

A ball of positive charge with negatively charged electrons distributed evenly throughout.

18
Q

Prior to the discovery of the electron

A

what was believed about the atom?

19
Q

Which experiment led to the plum-pudding model being discarded?

A

Rutherford’s alpha-scattering experiment.

20
Q

What is the currently accepted model of the atom?

A

The Bohr nuclear model.

21
Q

What were the conclusions of Rutherford’s alpha-scattering experiment?

A
  1. Most of the mass is concentrated in the nucleus. 2. The nucleus is positively charged.
22
Q

What reinforces a scientific theory?

A

When experimental results agree with theoretical predictions.

23
Q

What did James Chadwick’s experiments prove?

A

The existence of neutrons.

24
Q

Why do unstable nuclei give out radiation?

A

To become more stable by undergoing radioactive decay.

25
Q

What is radioactive decay?

A

The process where an unstable nucleus emits radiation to become more stable.

26
Q

Define the activity of an unstable nucleus.

A

The rate of decay of a source of unstable nuclei.

27
Q

What is the unit of radioactive activity?

A

Becquerel (Bq).

28
Q

What is count-rate?

A

The number of radioactive decays per second for a radioactive source.

29
Q

Give an example of a detector used to measure count-rate.

A

Geiger-Muller tube.

30
Q

What are the four types of nuclear radiation?

A
  1. Alpha particles 2. Beta particles 3. Gamma rays 4. Neutrons
31
Q

What are the constituents of an alpha particle?

A

Two protons and two neutrons (same as a helium nucleus).

32
Q

What is the range of an alpha particle through air?

A

A few centimetres (typically 2-10 cm).

33
Q

What will stop beta radiation?

A

A thin sheet of aluminium or several metres of air.

34
Q

What will stop gamma radiation?

A

Several centimetres of lead or a few metres of concrete.

35
Q

Which type of radiation is most ionising?

A

Alpha radiation.

36
Q

Which type of radiation is least ionising?

A

Gamma radiation.

37
Q

State any changes to mass or charge due to emission of a gamma ray.

A

Both mass and charge remain unchanged.

38
Q

Describe the nature of radioactive decay.

A
  • Random. - Which nucleus decays and when is determined by chance.
39
Q

Define the half-life of a radioactive isotope.

A
  1. The time it takes for the number of unstable nuclei in a substance to halve. 2. The time it takes for the count rate to halve.
40
Q

What is radioactive contamination?

A

The presence of unwanted radioactive nuclei on other materials.

41
Q

What is irradiation?

A

The process of exposing a material to nuclear radiation (the material does not become radioactive).

42
Q

Why is it important to publish studies on the effects of radiation?

A

To allow findings to be independently checked (peer review).

Physics (7 decks)

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