2b.2 - Electronic structure

Question 1

Describe the experiment that disproved the plum pudding model of the atom

Answer 1

• Fired a beam of alpha particles at thin gold foil

Question 2

What did they expect from the experiment that disproved the plum pudding model?

Answer 2

Positively charged alpha particles would be slightly deflected by the electrons in the plum pudding model

Question 3

What actually happened in the Rutherford experiment that disproved the plum pudding model?

Answer 3

Most alpha particles went straight through but the odd one came straight back at them

Question 4

What is an isotopes?

Answer 4

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

Question 5

Why is radioactivity random?

Answer 5

• You can’t say when a nuclei is going to decay

- You can’t make decay happen

Question 6

What is the three different types of radiation?

Answer 6

Alpha, beta, gamma

Question 7

What is background radiation?

Answer 7

Radiation that is present at all times, all around us

Question 8

Where does background radiation come from? (3)

Answer 8

• Unstable isotopes
• Radiation from space
• Radiation due to man made sources

Question 9

What relative proportion of background radiation is radon gas?

Answer 9

51%

Question 10

What relative proportion of background radiation is cosmic rays?

Answer 10

10%

Question 11

What relative proportion of background radiation is rocks and building materials?

Answer 11

14%

Question 12

What relative proportion of background radiation is from nuclear industry?

Answer 12

1%

Question 13

What relative proportion of background radiation is medical x-rays?

Answer 13

12%

Question 14

What relative proportion of background radiation is food?

Answer 14

12%

Question 15

What is an alpha particle? (2)

Answer 15

• A helium nuclei

- Two protons, two neutrons

Question 16

How far can alpha particles travel?

Answer 16

They are stopped quickly, even when travelling through air

Question 17

What are beta particles?

Answer 17

Fast moving electrons

Question 18

How ionising are beta radiation?

Answer 18

Strongly ionising

Question 19

How far can beta particles travel?

Answer 19

• Long range in air

- Penetrate moderately into materials

Question 20

What is gamma radiation?

Answer 20

A very short wavelength of an EM wave

Question 21

How far can gamma rays travel? (2)

Answer 21

• Penetrate far into materials without being stopped

- pass straight through air

Question 22

How ionising are gamma rays?

Answer 22

Weakly ionising

Question 23

What do gamma rays not have?

Answer 23

A mass and a charge

Question 24

What are the products of alpha decay?

Answer 24

• A helium neucli
• A gamma ray
• The new atom it makes

Question 25

How do you know what new atom is made in alpha decay?

Answer 25

Take 4 from the mass number and two from the atomic number

Question 26

What is made as products of beta decay?

Answer 26

- A new atom | - A beta particle

Question 27

How do you know what new atom is made in beta decay?

Answer 27

Add 1 to the atomic number

Question 28

Write the nuclear equation for the alpha decay of uranium 238 U 92

Answer 28

238. 234. 4. 0 U -> Th. +. He. + Y 92. 90. 2. 0

Question 29

Write the nuclear equation for the beta decay of Carbon-14 14 C 6

Answer 29

14. 14. 0 C ->. N. + e 6 7. -1

Question 30

What charge do alpha particles have?

Answer 30

Positive

Question 31

What charge do beta particles have?

Answer 31

Negative

Question 32

What are alpha and beta particles deflected by?

Answer 32

Electric and magnetic fields

Question 33

Why are alpha and beta particles deflected in opposite directions by magnetic or electric fields?

Answer 33

They have opposite charges

Question 34

Why are alpha particles deflected less even though they have a stronger charge?

Answer 34

They have a much greater mass

Question 35

Why is gamma radiation not deflected by electric and magnetic fields?

Answer 35

Gamma radiation has no charge

Question 36

What does radiation dose depend on?

Answer 36

- Type | - Amount

Question 37

The higher the radiation dose ...

Answer 37

...the more at risk you are of developing cancer

Question 38

What do radiographers do to protect themselves from radiation?

Answer 38

Wear lead aprons and stand behind lead screens

Question 39

What was the plum pudding model?

Answer 39

- Atoms were spheres of positive charge | - Tiny negative electrons stuck in it like plums in a plum pudding