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Physics > P6.1 > Flashcards

P6.1 Flashcards

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1
Q

What determines the charge of a nucleus?

A

Number of protons in the nucleus

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2
Q

How can the mass of the nucleus change without the charge changing?

A

The number of neutrons in the nucleus

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3
Q

What is a stable atom?

A

Means they don’t break down or decay

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4
Q

What do unstable nuclei do?

A

Emit radiation that is made up particles or waves
Radioactive nucleus

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5
Q

What are the different types of radiation?

A

Alpha - particle, nucleus of a helium atom
Beta - particle, fast moving electron
Gamma - electromagnetic wave, wave of the electromagnetic spectrum
Neutron - particle, particle in the nucleus

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6
Q

Where does the fast-moving electron come from?

A

When neutrons are unstable they can decay into a proton and electron

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7
Q

How do you detect radiation?

A

Geiger counter
Device that clicks when radiation enteres it
Each click is a tiny current produced when radiation ionises atoms of gas inside the tube

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8
Q

What does penetration mean?

A

If it can go through it

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9
Q

What stops alpha radiation?

A

A few sheets of paper or skin

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10
Q

What can beta penetrate and what can stop it?

A

Can penetrate a few sheets of paper
Blocked by a few mm of aluminium

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11
Q

What can gamma penetrate and what can stop it?

A

Most penetrating radiation
Penetrates - few sheets of paper, aluminium
Most of it is stopped by a few cm of lead but some can still get through

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12
Q

What does ionising radiation mean?

A

Radiation can remove electrons from atoms to produce positively charged ions

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13
Q

What are the relative masses and charges of the types of radiation?

A

Alpha - large, +2
Beta - small, -1
Gamma - none, none

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14
Q

What is the ionising power and range of the types of radiation?

A

Alpha - high, short
Beta - medium, medium
Gamma - low, long

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15
Q

Why is the alpha range of radiation low?

A

Energy needs to be transferred to an atom to ionise it
Alpha particles transfer more energy to the material they’re travelling through so the range is shorter

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16
Q

What happens in alpha decay

A

Large nuclei are unstable
Two protons and two neutrons can join up to form an alpha particle which is emitted from the nucleus

17
Q

What is the equation for nuclear decay?

A

Example:
240 PU > 236 U + 4He
94 92 2
Must make sure the equation is balanced, mass is conserved
Top numbers must add up
And charges must add up, charge is conserved

18
Q

What happens in beta decay?

A

A neutron decays to a proton and an electron
Electron is emitted as a beta particle
Number of neutrons goes down by one but number of protons goes up by one

19
Q

What is the nuclear equation for beta decay?

A

14 C > 14 N + 0 e
6 7 -1
Total number of protons and neutrons in the nucleus doesn’t change so mass stays the same
Charge is increased by 1 but particle with charge of -1 is emitted so charge stays the same

20
Q

What happens in gamma decay?

A

Gamma rays are electromagnetic waves so don’t have a mass or charge
Gamma ray is emitted with an Alpha or beta particle so atomic and mass number usually stays the same

21
Q

What happens in neutron emission?

A

When some nuclei decay they produce nuclei with large numbers of neutrons
These nuclei can emit neutrons
Nucleus becomes more stable

22
Q

What is the nuclear equation for neutron emission?

A

5 He > 4 He + 1 n
2 2 0

23
Q

How is radiation emitted?

A

Randomly

24
Q

What is the activity of a sample and what is it measured in?

A

Radiation emitted per second
Becquerels (Bq)

25
Q

What is half-life?

A

The time it takes for the activity of radioactive material to halve
Half-life is constant

26
Q

What is the net decline?

A

The ratio of the final to initial activity

27
Q

Why do electrons not spiral into the nucleus as they’re attracted to each other?

A

Electrons only occupy certain specified energy levels around the nucleus of an atom
Different atoms have different energy levels
Electrons usually occupy the lowest energy level possible at the smallest distance from the nucleus

28
Q

What are photons?

A

When electromagnetic radiation is emitted and absorbed as packets of energy

29
Q

What happens when the electron is ‘excited’?

A

When the photon has the right amount of energy the electron moves from a lower to higher level of energy

30
Q

What is the absorption spectrum?

A

Shows a set of frequencies of radiation absorbed by an atom when excited

Physics (9 decks)

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