Radioactivity Model Questions and Solutions

Define radioactivity

The spontaneous decay of an atomic nucleus with the emission of different types of radiation e.g. alpha, beta or gamma.

2. What change takes place in the nucleus of an atom when beta decay occurs?

A neutron changes into a proton and an electron is emitted from the nucleus.

4. What are isotopes?

Atoms with the same atomic number but different mass number due to the different number of neutrons.

What is a radioisotope?

An isotope with an unstable nucleus

6. Define the half life

The time taken for half the sample to decay.

Give two differences between chemical reactions and nuclear reactions

Chemical: No change to nucleus, bonds are broken or formed.

Nuclear: No bond breaking or forming and new elements formed (transmutation)

9. Give two properties of beta particles

Can be stopped by 5mm aluminium and high speed.

10. State one risk associated with alpha radiation

Cancer or mutations. However this is only if it can penetrate skin - which it cannot.

Smoke detectors are fitted with the isotope Americium - 241. Why is this relatively safe?

The alpha particles emitted cannot penetrate skin.

12. Give two properties of alpha particles

Low speed and poor penetration. Skin can stop the particles.

13.Explain how the carbon -14 isotope allows certain archaeological

discoveries to be dated In living things, the ratio of carbon-12 to carbon-14 is constant however this ratio changes with age.

Carbon-14 decreases since death.

14. What are alpha particles?

Helium nucleus. Two protons and two neutrons

15. What are gamma particles? Provide two properties

Electromagnetic radiation. Highly penetrating and can only be stopped by thick lead.