P4 Isotopes and Nuclear Radiation (page 196)

Question 1

What are Isotopes?

Answer 1

They are different forms of the same element.

Question 2

All atoms of each element have the set number of what?

Answer 2

Protons (so each nucleus has a given positive charge).

Question 3

The number of protons in an atoms is called?

Answer 3

Atomic number

Question 4

What is the mass number of an atom (the mass of the nucleus)?

Answer 4

it is the number of protons + the number of neutrons in its nucleus.

Question 5

What are Isotopes of an element?

Answer 5

they are atoms with the same number of protons (the same atomic number, and so the same charge on the nucleus) but a different number of neutrons (a different mass number)

E.g. ¹⁸
O is an isotope of oxygen.
⁸

Question 6

Draw a diagram showing Every oxygen atom has 8 protons?

Answer 6

See picture 1 on page 196 for result.

Question 7

do all elements hae different isotopes?

Answer 7

Yes, but there are usually only one or two stable ones.

Question 8

What happens to the unstable isotopes?

Answer 8

they tend to decay into other elements and give out radiation as they try to become more stable.

Question 9

How do unstable isotopes try to become stable?

Answer 9

they try to become more stable by trying to balance the number of protons and neutrons in their nucleus or get rid of any excess energy)

This process is called radioactive decay.

Question 10

Radioactive substances spit out one or more types of ionising radiation from their nucleus, what are they called?

Answer 10

Alpha, Beta & Gamma radiation.

Question 11

Radioactive substances can also release neutrons (n) when they decay, why?

Answer 11

to rebalance the number of protons and neutrons.

Question 12

What is Ionising Radiation?

Answer 12

it is Radiation that knocks electrons off atoms, creating positive ions. The ionising power of a radiation source is how easily it can do this.

Question 13

What are Alpha Particles?

Answer 13

They are Helium Nuclei

Question 14

What is Alpha Radiation?

Answer 14

it is when an Alpha particle (α) is emitted from the nucleus. An α-particle is two neutrons and two protons (like a helium nucleus)

They don’t penetrate very far into materials and are stopped quickly - they can only travel a few cm in air and are absorbed by a sheet of paper.

Because of their size they are strongly ionising.

Question 15

Where is Alpha radiation used?

Answer 15

in smoke detectors - it ionises air particles causing a current to flow. If there is smoke in the air it binds to the ions - meaning current stops and the alarm sounds.

Question 16

What are Beta Particles?

Answer 16

High-speed Electrons e-

Question 17

What is a Beta Particle (β)

Answer 17

It is simply a fast moving electron released by the nucleus.

Question 18

What is Beta radiation?

Answer 18

They are moderately ionising. They penetrate moderately far into materials before colliding and having a range in air of a few metres. They are absorbed by a sheet of alumiium (around 5 mm)

For every beta particle emitted, a neutron in the nucleus has turned into a proton (see page 197).

Question 19

Where is Beta radiation used?

Answer 19

Beta emitters are used to test the thickness of sheets of metal, as the particles are not immediately absorbed by the material like alpha radiation and would be and do not penetrate as far as gamma rays.

Question 20

What are Gamma Rays (γ)

Answer 20

They are EM Waves with a short wavelength.

Gammy rays are waves of electromagnetic radiation (see page 220) released by the nucleus.

Question 21

What do Gamma Rays do?

Answer 21

They penetrate far into materials without being stopped and will travel a long distance through air.

This means they are weakly ionising because they tend to pass through rather than collide with atoms. Eventually they hit soething and do damage.

They can be absorbed by thick sheets of lead or metres of concrete. (uses of gamma rays are on page 224).

Question 22

In order to sterilise medical equipment, radiation is directed at the equipment while it is sealed in packaging. Explain whether alpha radiation would be suitable for this use (2 marks)

Answer 22

Alpha would not be suitable because it is stopped by a few cm of air or a sheet of paper (1 mark) TIt would not be able to pass through the packaging to sterlise the equipment (1 mark).

(Remember, knowing different kinds of radiation and what can absorb them often bags you a few easy marks in an exam).