Atomic structure and radioacticity Flashcards

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1
Q

What is the radius of an atom?

A

……….-10…..

1 x 10…..m..

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2
Q

What is the radius of the nucleus?

A

It is less than 1 / 10 000 of the radius of the atom.

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3
Q

Do energy levels further away from the nucleus have more or less energy?

A

HIGHER energy than those which are CLOSER to the nucleus.

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4
Q

What is an isotope?

A

They are atoms of the same element with a different number of NEUTRONS.

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5
Q

What is a alpha particle?

A

The same as a HELIUM NUCLEUS (two protons joined to two neutrons).

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6
Q

What is a beta particle?

A

An ELECTRON which is EJECTED from the nucleus at very high speed.

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7
Q

What do some isotopes have?

A

An UNSTABLE nucleus.

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8
Q

How do unstable isotopes become stable?

A

The nucleus gives out RADIATION (RADIOACTIVE DECAY).

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9
Q

What is meant by activity?

A

The rate at which a sourece of unstable nuclei decay.

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10
Q

What is activity measured in?

A

Becquerel (Bq) 1 Bq = 1 decay per second.

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11
Q

What can we use to measure activity?

A

Geiger-Muller tube.

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12
Q

What happens in beta decay?

A

A NEUTRON changes into a PROTON and an ELECTRON.

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13
Q

What is gamma radiation?

A

Gamma rays are a type of ELECTROMAGNETIC RADIATION from the nucleus.

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14
Q

What are alpha particles stopped by?

A

A single sheet of paper.

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15
Q

What are beta particles stopped by?

A

A FEW MILLIMETRES OF ALUMINIUM.

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16
Q

What is gamma radiation stopped by?

A

SEVERAL CENTIMETRES OF LEAD.

17
Q

What can cause radiation to form ions?

A

When radiation COLLIDES with atoms. (causing atoms to lose electrons forming ions)

18
Q

How ionising are alpha particles?

A

VERY STRONGLY IONISING.

19
Q

How ionising are beta particles?

A

QUITE STRONGLY IONISING.

20
Q

How ionising is gamma radiation?

A

WEAKLY IONISING.

21
Q

What two rules are there for alpha decay?

A

1) The ATOMIC NUMBER DECREASES BY 2.

2) The MASS NUMBER DECREASES BY 4.

22
Q

Whats the rule for beta decay?

A

The ATOMIC NUMBER INCREASES BY 1 but the mass number does not change.

23
Q

How can scientists predict when a nucleus will decay?

A

The can’t, decay is a RANDOM process.

24
Q

What is meant by half-life?

A

It is the time it takes for the number of NUCLEI of the isotope in a sample to HALVE.

25
Q

What is Irradiation?

A

Exposing an object to NUCLEAR RADIATION (alpha, beta, gamma or neutrons).

26
Q

Give one use gamma radiation?

A

Sterilisation of objects.

27
Q

What is radioactive contamination?

A

When UNWANTED RADIOACTIVE ISOTOPES end up on other materials.