Physics- Radioactivity And Particles

Question 0

What is the mass number ?

Answer 0

Total number of protons and neutrons in the nucleus

Question 1

What is the atomic number?

Answer 1

Number of protons

Question 2

What are isotopes?

Answer 2

Atoms with the same number of protons but different number of neutrons

Question 3

Where does background radiation come from?

Answer 3

Radioactive rocks
Space - the sun
Human activity - nuclear explosions, nuclear waste

Question 4

What are alpha particles?

Answer 4

Helium nuclei :
4
He
2

Question 5

What are beta particles?

Answer 5

Electrons :

0
e
-1

Question 6

What are gamma rays?

Answer 6

Very short wavelength EM waves

Question 7

Why does an isotope tend to be radioactive?

Answer 7

It has an UNSTABLE nucleus so it DECAYS and emits RADIATION

Question 8

Alpha particles

What is it made up of
Ionising power
Penetrating power- blocked by what
Charge
Result of emitting an alpha particle

Answer 8

Made up of 2 protons and 2 neutrons

Strong ionising power

Weak penetration power- blocked by paper, skin, few cm of air

Positively charged- deflected by electric and magnetic fields

Emitting an alpha particle DECREASES ATOMIC NO. BY 2 and MASS NUMBER BY 4

Question 9

Beta particles

Ionising power
Penetrating power - blocked by what
Result of emitting beta particle
Charge

Answer 9

Moderate ionising power
Moderate penetrating power- blocked by thin metal

ATOMIC NO. DECREASES BY 1, mass number stays the same

Negatively charged - electron - deflected by electric and magnetic fields

Question 10

Gamma rays

Mass?
Ionising power
Penetrating power - blocked by what
Charge
Result in emission
Why emitted

Answer 10

No mass JUST ENERGY
Weak ionising power
High penetrating power - blocked by lead/concrete
No charge, not deflected
No effect on atomic number or mass number
If a nucleus has excess energy, energy lost by emission of gamma ray

Question 11

What did JJ Thomson discover

Answer 11

Electrons could be removed from atoms and atoms were spheres of positive charge with electrons stuck in them

Question 12

Who thought of the plum pudding model

Answer 12

JJ Thomson

Question 13

Who discovered that the plum pudding model was wrong and how

Answer 13

Hans Geiger and Ernest Marsden

Fired alpha particles at thin gold foil, most went straight through and hit a zinc sulphide screen but one alpha particle came straight back at them

Question 14

Who came up with a nuclear model of the atom

Answer 14

Ernest Rutherford

Question 15

What does the nuclear model of the atom say and why

Answer 15

• most of the mass is in centre and most of atom is empty space
• nucleus very small bc. Very few alpha particles deflected by much
• nucleus must be positive to repel alpha particles

Question 16

Alpha emission nuclear equation

226 ? ?
Ra ——-> Rn + He
88 ? ?

Answer 16

226 222 4
Ra ——-> Rn + He
88 86 2

Question 17

Beta emission nuclear equation

187 ? ?
Re ——-> Os + e
75 ? ?

Answer 17

187 187 0
Re ——-> Os + e
75 76 -1

Question 18

Gamma emission nuclear equation

99 ? ?
Tc ——-> Tc + ➰
43 ? ?

Answer 18

99 99 0
Tc ——-> Tc + ➰
43 43 0

Question 19

Gamma and alpha emission nuclear equation

238 ? ? ?
U ——-> Th + He + ➰
92 ? ? ?

Answer 19

238 234 4 0
U ——-> Th + He + ➰
92 90 2 0

Question 20

What is half-life?

Answer 20

The time taken for half of the radioactive nuclei to decay

Question 21

What detects radioactivity

Answer 21

A Geiger-Muller detector (GM)

Question 22

Uses of gamma radiation

Answer 22

Medical tracers (also beta)
Industrial tracers
Age of rocks, fossils

Question 23

How to protect yourself when working with radioactive materials?

Answer 23

Never allow skin contact
Hold with tongs and at arms length
Point away from body 
Avoid looking at it
Place in sealed lead box when not in use

Question 24

How people who regularly work with radioactivity protect themselves?

Answer 24

Wear lead aprons
Stand behind lead screens during procedures
Wear full protective suits to prevent radioactive particles being inhaled or lodging onto skin
Use remote controlled robot arms to carry out tasks in highly radioactive areas

Question 25

What is nuclear fission?

Answer 25

The splitting of an atom which releases energy

Question 26

What is usually split in a nuclear reactor in a nuclear power station? When does it split?

Answer 26

Uranium-235

If a slow moving neutron gets absorbed by a uranium-235 nucleus, the nucleus can split.

Question 27

What is a chain reaction?

Answer 27

When a uranium-235 nucleus splits, a small number of neutrons is released
These neutrons hit other uranium-235 nuclei, causing them to split and release more neutrons
Which hit more nuclei
And so on

Question 28

What happens when a uranium-235 splits?

Answer 28

It will form two new daughter nuclei (lighter elements than uranium, also radioactive)
Lots of energy given out in form of KE
Neutrons released

Question 29

In a nuclear reactor, what does a moderator do and what is it made out of?

Answer 29

Slows neutrons so that they can successfully collide with uranium nuclei and SUSTAIN chain reaction

Made out of graphite/water

Question 30

Control rods, function and what is it made out of?

Answer 30

Limit the rate of fission by absorbing excess neutrons

Made of Boron

Question 31

Steps to a gas-cooled nuclear reactor

Answer 31

1. Free neutrons collide with uranium atoms, temperature in reactor rises
2. Chain reaction sustained by moderator (graphite/water)
3. Control rods (boron) limit rate of fission
4. Gas (typically CO2) pumped through reactor to carry heat generated into HEAT EXCHANGER
5. In heat exchanger, energy given to water
6. Water heated -> steam -> turns turbine -> turns generator -> electricity