Atomic and Nuclear Physics

Question 1

What was the Plum Pudding model?

Answer 1

Proposed by J.J. Thompson. In this model, the atom was imagined to be a sphere of positive charge with negatively charged electrons dotted around inside it like plums in a pudding

Question 2

Charge, mass and position of a electron, proton and neutron

Answer 2

Electron - -1, 1/1840, orbital shells
Proton - 1, 1, Nucleus
Neutron - 0, 1, Nucleus

Question 3

Isotope definition

Answer 3

Atoms of the same element that have the same number of protons in their nucleus, but different number of neutrons

Question 4

Radioactive definition

Answer 4

Disintegration of unstable nuclei by emitting alpha-particles, beta-particles, or gamma radiation randomly and spontaneously

Question 5

What is a Alpha particle?

Answer 5

It’s the same as a helium nucleus consisting of 2 protons and 2 neutrons

Question 6

What is a beta particle?

Answer 6

It’s the same as a very fast electron

Question 7

What is gamma radiation?

Answer 7

It’s not a particle but a high energy electron magnetic wave

Question 8

Mass and charge of alpha, beta and gamma

Answer 8

A - 4, +2
B - 1/1840, -1
G - 0, 0

Question 9

What is the Alpha decay equation?

Answer 9

When an isotope decays by alpha emission, it loses two protons and two neutrons, meaning the atomic number decreases by 2 and the mass number decreased by 4

Question 10

What is the Beta decay equation

Answer 10

When an isotope decays by beta emission, the Atomic Number increases by one but the mass number stays the same. A neutron inside the nucleus turns into a proton and an electron

Question 11

What is the gamma equation?

Answer 11

Gamma radiation is an electromagnetic wave of very short wavelength. It carries only energy but no mass or charge and therefore has no effect on the atomic number or mass

Question 12

What is background radiation?

Answer 12

Background activity is detected when no radioactive sources are present, and the measured activity from a radioactive source has to be corrected by subtracting the background activity

Question 13

Where does background radiation come from?

Answer 13

Mostly from radon gas which is formed from other isotopes in rocks. Cosmic rays from the sun and organic material we eat because carbon, potassium and chloride all have radioactive isotopes

Question 14

What are some health risks to Nuclear radiation?

Answer 14

1. Alpha radiation is not as dangerous if the radioactive source is outside the body, because it cannot pass through the skin and is unlikely to reach cells inside the body
2. Beta and gamma radiation can penetrate the skin and cause damage to cells
3. Alpha radiation will damage cells if the radioactive source has been breathed in or swallowed

Question 15

Make a list of precautions that anyone working with radioactive sources could take to help protect themselves

Answer 15

Screens
Robotics
Distance
Time (exposure)

Question 16

How to measure the background radiation in a room?

Answer 16

1. Remove all known sources of radiation
2. Switch on a Geiger Müller tube and leave it for a period of time
3. Divide the count by the time and this will give you the background radiation as counts per minute

Question 17

What is Alpha decay stopped by?

Answer 17

It’s not very penetrating and is stopped by a few cm of air or by a sheet of paper

Question 18

What can beta radiation by stopped by?

Answer 18

More penetrating then alpha and can be stopped by a thin sheet of aluminium

Question 19

What is gamma radiation stopped by?

Answer 19

It’s very penetrating but can almost be stopped by thick lead

Question 20

Definition of half life

Answer 20

The half life of a radioactive material is the time taken for half of the unstable nuclei to decay