4. Atomic Structure (structure and development of the atom, nuclear equations, nuclear radiation properties)

Question 1

What did John Dalton do (1804)?

Answer 1

He believed that atoms were tiny spheres that could not be broken down

Question 2

What did JJ Thompson do (1904-1905)?

Answer 2

Thompson discovered electrons, so he said atoms were a ball of positive charge with electrons scattered in the atom (plum pudding model)

Question 3

What is Rutherford (1909)?

Answer 3

Rutherford and Marsen did the scattering experiment and realised most of the atom is empty space

Question 4

What are the observations and conclusions of the alpha particle scattering experiment?

Answer 4

Most went straight through so most of the atom is empty space
Some deflected less than 90 degrees meaning that the nucleus is positively charged
Few deflected more than 90 degrees so most of the mass is in the nucleus

Question 5

What are the subatomic particles charge and mass?

Answer 5

Electron: -1, 1/2000
Proton: +1, 1
Neutron: 0, 1

Question 6

What are isotopes?

Answer 6

A different version of the same element with the same number of protons different numbetr of neutrons

Question 7

What is radioactive decay?

Answer 7

when a nucleus decays, it is a random process

Question 8

What are the 4 types of decay?

Answer 8

• Alpha decay
• Beta decay
• Gamma decay
• Neutron decay

Question 9

What is radioactive substance?

Answer 9

Is an unstable nucleus which becomes stable from releasingly radiation

Question 10

What is alpha radiation?

Answer 10

• An alpha particle is a helium nucleus
• An alpha particle has 2 protons and 2 neutrons
• When a nucleus emits (gets rid of) on an alpha, it loses 2 of its neutrons and 2 of its protons
• So mass number decreases by 4
• Atomic number decreases by 2

Question 11

What happens to the mass number and atomic number in alpha decay?

Answer 11

• The mass number decreases by 4
• Atomic decreases by 2

Question 12

What is beta decay?

Answer 12

when a beta particle is emitted from the nucleus when a neutron turns into a proton

Question 13

What happens to the mass number and atomic number in beta decay?

Answer 13

• The mass number stays the same
• The atomic number increases by 1

Question 14

What is gamma decay?

Answer 14

• Gamma rays are electromagnetic waves, with a short wave length and a high frequency
• Because rays are electromagnetic waves, they don’t have a mass or charge
• When a nucleus emits a gamma ray its mass and atomic number don’t change

Question 15

When do gamma rays occur?

Answer 15

• When a nucleus is in its excited state
• When an excited nucleus emits a gamma ray it moves to a lower energy level

Question 16

What is an alpha particles charge?

Answer 16

+2

Question 17

What is a beta particles charge?

Answer 17

-1

Question 18

What is a gamma particles charge?

Answer 18

0

Question 19

What is an alpha particles range in air?

Answer 19

Few cms in air

Question 20

What are beta particles range in air?

Answer 20

A metre

Question 21

What are gamma particles range in air?

Answer 21

Infinite

Question 22

What is alpha particles penetration stopped by?

Answer 22

Stopped by paper

Question 23

What are beta particles penetration stopped by?

Answer 23

Stopped by a few mm of aluminium

Question 24

What are gamma particles penetration stopped by?

Answer 24

Reduced by a few mm of lead

Question 25

What are alpha particles ionisation?

Answer 25

High

Question 26

What are beta particles particles ionisation?

Answer 26

Medium

Question 27

What are gamma particles ionisation?

Answer 27

Low

Question 28

What is ionising power?

Answer 28

Turning other atoms in ions by ‘knocking’ their electrons. Determined by charge and size

Question 29

What is Ionisation?

Answer 29

Any process from where atoms are charged

Question 30

What is a beta particle?

Answer 30

A beta particle is a fast moving electron