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Physics Gcse > Radioactivity- 6 > Flashcards

Radioactivity- 6 Flashcards

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1
Q

What did Ernest Rutherford do that proved the plum pudding model wrong?

A

Conducted an experiment where he fired positively charged subatomic particles (alpha particles) through gold foil. He discovered that while most went through, some bounced back which is how he discovers the positively charged nucleus and electrons moving around it while most of the atom being empty space.

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2
Q

Proton

A

Location- nucleus
Relative charge +1
Relative mass 1

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3
Q

Neutron

A

Location: nucleus
Relative charge: 0
Relative mass: 1

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4
Q

Electron

A

Location: shells
Relative charge: -1
Relative mass: 0/ 1 over 1835

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5
Q

If the atom absorbs energy:

A

The electron can move to a higher orbit (outer shells)

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6
Q

When an electron returns to a lower orbit

A

the atom emits energy as electromagnetic radiation (visible light of a particular wavelength.)

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7
Q

Ionising radiation

A

Radiation that causes electrons to escape an atom.

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8
Q

Main source of background radiation

A

Radon gas

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9
Q

Other radiation

A 
Food and drink
buildings and ground
Cosmic rays
Medical (gamma+ xrays)
Nuclear
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10
Q

How is radioactivity of a source measured?

A

Geiger- Müller tube
Radiation passing through the tube ionises gas inside it and allows a short pulse of current to flow.
This tube can either be connected to a counter to count the pulses of current or can produce a click each time radiation is detected.
The count rate is the number of clicks per second or minute.

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11
Q

What do scientists need to do before measuring the radiation of a source?

A

Measure the background radiation several times and calculate the mean then subtract this from their reading of the radiation of a source.

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12
Q

Half life

A

The average time it takes for the number of radioactive nuclei in an isotope to halve

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13
Q

Alpha decay

A 
He
Atomic mass (top number decreases) by 4
Atomic number (bottom number) decreases by 2
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14
Q

Beta decay

A 
e
Atomic mass (top number) stays the same
Atomic number (bottom number) increases by 1
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15
Q

Positron (beta plus) decay

A 
e
Atomic mass (top number) stays the same 
Atomic number (bottom number) decreases by 1
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16
Q

How does nuclei lose energy when subatomic particles in the nucleus are rearranged

A

As gamma radiation

Helps to make nuclei more stable

17
Q

Half life of isotope uranium-235

A

700 million years

18
Q

Half life of isotope carbon-14

A

5730 years

19
Q

Half life of isotope caesium-137

A

30 years

20
Q

Half life of isotope radon-222

A

3.8 days

21
Q

The more stable nuclei a sample contains, the lower its —

The half life of an isotope is also a measure of how long it takes for the activity to —

A

Activity

Halve

22
Q

What can small amounts of ionising radiation over long periods of time cause?

A

Damage DNA inside the cell and cause mutations

Cancer

23
Q

How are risks of radiation contamination reduced in hospitals

A

Storing radioactive sources in lead-lined containers
Distance from a source (using tongs)
Shielding from the source
Minimising time in the presence of a source

24
Q

What happens when someone is irradiated

A

They’re exposed to alpha, beta or gamma radiation from nearby radioactive materials. Once a person moves away the irradiation stops

25
Q

What happens when someone is contaminated

A

They get particles of radioactive material on their skin or in their body. They’ll be exposed to radiation as the unstable isotopes in the material decay. This will continue until the material has decayed or until the source of contamination is removed but this isn’t always possible. Water and soils can be contaminated and spread through the food chain.

26
Q

Plum pudding model

A

Positively charged pudding

27
Q

Radius of nucleus and atom

A

Nucleus: 1 times 10^-15 m

Atom : 1 times 10^-10 m

28
Q 
Alpha particles 
How many protons and neutrons 
Relative mass
How many electrons 
Charge
How far will they travel in air
How ionising 
What are they stopped by
A 
2 protons and 2 neutrons 
Relative mass of 4
No electrons so charge is +2
Written as a or ^42He
Travel a few cm in air as they lose energy quickly 
Very ionising 
Stopped by sheet of paper
29
Q 
What are beta particles 
Relative mass 
Charge 
Where do the electrons that are beta particles come from 
How far will they travel in air
How ionising 
What are they stopped by
A 
High energy, high speed electrons 
Relative mass is 1/1835
Charge is -1
They come from the nucleus of atoms when a neutron transforms to a proton. Beta particles don’t ionise the atom as they leave them.
Travel a few metres in air
Moderately ionising 
Stopped by 3mm thick aluminium because they’re less ionising than alpha particles so lose less energy ionising particles they encounter- so they have more energy to travel through thicker materials.
Gains 1 electron
B-  or ^0 -1 e
30
Q

What are positrons
Mass
Charge

A 
High energy high speed particles 
Same as electrons 1/1835
Charge +1
Lose 1 electron 
B+ or. ^0 +1 e
31
Q 
What are gamma rays 
What are their charge 
How far do they travel in air
How ionising 
What are they stopped by
A 
High frequency electromagnetic waves
Don’t have an electric charge 
Travel a few km in air 
Weakly ionising 
Stopped by lead few cm thick
32
Q

Isotopes of the same element

A

Same atomic number (bottom number) number of protons

Different mass number (top number) if different numbers of neutrons

33
Q

How is a positive ion formed

A

An atom has the same number of protons and electrons so has no charge. If an atom loses an electron, it then has one more proton than it electron so has an overall positive charge. When an atom gains an electron the overall charge is negative because there’s one more electron than proton and electrons have a negative charge.

Physics Gcse (15 decks)

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