National 5 Chemistry- Unit 3: Nuclear Chemistry

question

What is a radioisotope?
answer

A radioactive isotope of an element
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What is the relationship between the stability and the atomic number of a element?
answer

As the atomic number increases the stability decreases.
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What does alpha radiation consist of?
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A helium nucleus. Charge:+2 Mass:4
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What does gamma radiation consist of?
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An electromagnetic spectrum wave. No charge or mass.
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What does beta radiation consist of?
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A fast moving electron. Charge:-1 Mass:0
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How can gamma radiation be stopped?
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By 10cm of lead or 0.1m of concrete
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How can alpha radiation be stopped?
answer

A sheet of paper
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How can beta radiation be stopped?
answer

Thin metal foil
question

How would the atomic number and mass number change if it emits an alpha particle?
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Atomic number would decrease by 2 Mass number would decrease by 4
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How would the atomic number and mass number change if it emits a beta particle?
answer

Atomic number would increase by 1 Mass number would stay the same
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How would the atomic number and mass number change if it emits gamma radiation?
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Atomic number would stay the same Mass number would stay the same
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How can radioactivity be measured?
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Using a geiger counter: tells number of particles detected per minute
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What does half-life mean?
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The time it takes for the mass of a radioisotope to halve.
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How does carbon dating work?
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Plants absorb CO2(with carbon-14) from atmosphere. When organism dies it stops absorbing CO2. The age of the organism can be calculated using the half life of carbon-14
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What are medical uses of radioisotopes?
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Technetium-99 used in diagnostic nuclear medicine: short half life, emits gamma rays-easily detected, can escape body Cobalt-60 used to treat tumours: 5 year half life- treatment remains active for long time, emits gamma
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How can leaks or blockages be detected in underground pipes?
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Material that emits gamma is put into pipe and detector above ground is moved along the pipe. If there is a leak the reading increases.
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What is the form of radiation used in smoke alarms and why is it used?
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Americium-241 because it has a long half life and emits alpha particles
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How do smoke alarms work?
answer

Alpha is contained in a metal ionisation chamber where it knocks electrons off atoms to ionise the air. Positively charged oxygen and nitrogen go to the negative plate while negatively charged electrons go to the positive plate making an electric current. Smoke particles attach to the ions, neutralise them and stop the current which triggers the alarm.

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