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Physics > Atoms , isotopes, radiation > Flashcards

Atoms , isotopes, radiation Flashcards

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1
Q

What is the radius of an atom?

A

1 X 10 ^-10m

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2
Q

How small is the radius of an atom’s nucleus?

A

1 X 10^-14m

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3
Q

How did Dalton describe the atom?

A

.Tiny spheres
.Indivisible and indestructible
.Made up all matter

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4
Q

Explain J.J Thomson’s model of the atom

A

Plum pudding
.Sphere of positive charge with negative electrons stuck in it
.Electrons could be removed

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5
Q

Explain Rutherford’s experiment and it’s results.

A

Alpha scattering experiment
-Fired a beam of alpha particles at thin gold foil expecting (from plum pudding model) for it to go straight through

Results and what it shows:
.Most alpha particles went straight through meaning that most of the atom is empty space
.A small number of alpha particles were deflected at large angles showing there is a concentration of positive charge (alpha= positive and like charges repel)
.A small number of alpha particles came straight back meaning the positive charge and mass are concentrated in a very small nucleus.

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6
Q

Who created the first nuclear model?

A

Ernest Rutherford

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7
Q

What did Niels Bohr discover about the atom?

A

Electrons orbiting the nucleus do so at certain distances called energy levels.

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8
Q

What did James Chadwick discover about the atom?

A

It had particles with no charge (neutron).

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9
Q

List the scientist that contributed to the atom in order

A

John Dalton
J.J Thomsom
Ernest Rutherford
Niels Bohr
James Chadwick

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10
Q

What are the relative charges of subatomic particles?

A

proton: +1
neutron: 0
electron: -1

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11
Q

What charge is the nucleus?

A

Positive

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12
Q

What is the charge of an atom?

A

Neutral

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13
Q

Explain how electrons can move within (or sometimes leave) the atom

A

If the electron gains energy by absorbing EM (electromagnetic) radiation, they move to a higher energy level, further from the nucleus.

If the electron releases EM radiation, it moves to a lower energy level, closer to the nucleus.

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14
Q

True or false:
There are the same number of protons and neutrons in an atom

A

False

same number of protons and electrons

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15
Q

What does the mass number show? Is it on top or bottom?

A

The number of protons and neutrons

top

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16
Q

Define an isotope

A

Atoms of the same element with the same number of protons but different number of neutrons

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17
Q

What happens if an atom loses an electron?

A

It becomes a positive ion (cation)

18
Q

Explain radioactive decay

A

Some atomic nuclei are unstable. The nucleus gives out radiation as it becomes more stable.

19
Q

Define activity

A

The rate at which a source of unstable nuclei decays.

20
Q

What is activity measured in?

A

Becquerels (Bq)

21
Q

Define count rate
What could you measure it with?

A

The number of decays each second by a detector e.g Geiger-Muller tube

22
Q

Describe the properties/composition of alpha particles including penetration and ionisation.

A

Alpha particle emitted from the nucleus
.2 protons, 2 neutron
. +2 charge
.travels a few cm in air, stopped by paper or skin
.high ionisation

23
Q

What is a beta particle? What’s it’s charge, penetration, ionisation?

A

A fast moving electron from the nucleus (neutron turns into a proton inside the nucleus and gives off an electron.

Charge: -1
Penetration: travels a few metres in air, stopped by a thin layer of aluminium
Ionisation: medium

24
Q

What is a gamma particle? What’s it’s charge, penetration, ionisation?

A

High energy electromagnetic wave. Usually follows alpha or beta decay.

Charge: 0
Penetration: travels kilometres in air, stopped by thick lead or concrete.
Ionisation: low

25
Q

True or false: alpha particles are the same as helium nuclei

A

True

26
Q

Give and explain an example of alpha radiation.
Why can’t we use beta or gamma radiation for this?

A

Smoke detectors
-> alpha radiation ionises the air particles causing current to flow. If there is smoke in the air, it binds to the ions, meaning the current stops and the alarm sounds.

Most of the beta and gamma radiation would penetrate smoke and no change in the count rate would be detected.

27
Q

Give an explain an example of beta radiation.
Why can’t we use alpha or gamma?

A

Testing the thickness of sheets of metal. If the foil is too thick it absorbs more beta particles. The detector receives less beta particles and then sends a signal to the rollers to increase the force on the foil, making it thinner.

If the foil is too thin it absorbs less beta particles. The detector receives more beta particles and then sends a signal to the rollers to decrease the force on the foil, making it thicker.

Alpha radiation would be blocked by even a thin sheet of paper, while gamma radiation will pass through most thin materials

28
Q

True or false: gamma rays change the charge and mass of the nucleus

A

False. There is no change to the mass number of atomic number.

29
Q

True or false: radiation is random

A

True

30
Q

Define half life

A

The time taken for half of the unstable nuclei in a sample to decay .

31
Q

Explain 2 reasons why there is background radiation

A

1) natural sources such as rocks and cosmic rays from space (mostly from the sun)
2)man-made sources such as the fallout from nuclear weapons
testing and nuclear accidents

32
Q

What is radiation dose measured in?

A

Sieverts

33
Q

Define irradiation

A

Exposing objects to beams of radiation

34
Q

True or false: we are irradiated.

A

True, by background radiation

35
Q

Define contamination

A

When an object has radioactive material introduced into it.

36
Q

Why is contamination dangerous?

A

The contaminating atoms might decay, releasing radiation which could cause you harm.

37
Q

How can you avoid contamination?

A

1) use gloves and tongs when handling sources
2)wear protective suits
3)point source away from you

38
Q

What are the risks to using radiation?

A

1)radiation can enter living cells and ionise atoms in them which can lead to tissue damage
2)lower doses tend to cause minor damage to cells which can lead to mutations which divide uncontrollably (cancer).
3) higher doses tend to kill cells causing radiation sickness

39
Q

Explain 2 uses for gamma radiation and how it works

A

1) Medical tracers
radioactive isotopes are injected into people and their progress around the body can be traced by an external detector. A computer shows where the strongest reading is.

2) Radiotherapy-treating cancer
gamma rays are directed at just the right dosage to kill the cancer cells

40
Q

Can nuclear fission be done on earth?

A

Yes

40
Q

What fuels are mostly used for nuclear fission?

A

Uranium and Plutonium

Physics (4 decks)

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