Past Exam Questions Flashcards Preview

Chemistry: 08 - Radioactivity > Past Exam Questions > Flashcards

Flashcards in Past Exam Questions Deck (15)
Loading flashcards...
1

Define radioactivity.

The spontaneous breaking up of unstable nuclei with the emission of one or more types of radiation

2

What change takes place in the structure of the nucleus of an atom when beta decay occurs?
3 points

A neutron in an unstable nucleus is converted into a proton and an electron
Atomic number increases by one
Mass number remains the same

3

Write a balanced equation for the beta decay of a carbon-14 nucleus

14C -> 14N + e-
carbon-14 -> nitrogen-14 + e-

4

What are isotopes?

Atoms of the same element i.e. have the same atomic number which have different mass numbers due to the different number of neutrons in the nucleus

5

What is a radioisotope?

A radioactive isotope

6

Define the half-life of a radioisotope.

The time taken for half of the nuclei in any given sample to decay

7

Give two differences between chemical reactions and nuclear reactions.

No new element is formed in a chemical reaction but a new element is formed in a nuclear reaction
There is no release of nuclear radiation in a chemical reaction but there is nuclear radiation released in a nuclear reaction

8

Give two properties of beta-particles
5 possible points

They are fast moving electrons
They are formed when a neutron in an unstable nucleus changes into a proton and an electron, this electron is then ejected from the nucleus as a beta-particle
They are lighter than alpha particles
They have a higher penetrating power than alpha particles
Can penetrate up to 5 mm of aluminium

9

State one risk associated with exposure to alpha radiation.

Ingestion or inhalation of alpha particles can damage the lungs, liver and kidneys and cause cancer

10

Explain why the occupants of a house fitted with smoke detectors containing americum-241 are not at risk from alpha radiation emitted by these devices.

Alpha particles cannot penetrate the skin and is stopped by a few centimetres of air

11

Explain whether or not the americum-241 in smoke alarms needs to be replaced regularly.

The half-life of americum-241 is 432 years and therefore it does not to be replaced regularly

12

Give two properties of alpha particles
6 possible points

They are groups of two protons and two neutrons stuck together
They carry a double positive charge
They are emitted from the unstable nucleus of a radioactive element
They have a relatively large mass
They travel relatively slow
They have a low penetrating power and are stopped by a sheet of paper or a few centimetres of air

13

Write an equation for the nuclear reaction involved in the beta decay of carbon-14

14C -> 14N + e-
carbon-14 -> nitrogen-14 + e-

14

Explain how the carbon-14 isotope allows certain archaeological discoveries to be dated
3 points

Carbon-14 decays by beta radiation but is continuously replaced when an organism is alive
When an organism dies the amount of carbon-14 present decreases but the amount of carbon-12 remains the same
Therefore, by measuring the ratio of carbon-14 to carbon-12 in the remains of a material scientists can date an object.

15

List the three types of radiation in order of increasing penetrating power

Alpha particles, beta particles, gamma radiation