atomic structure

Question 1

alpha?

Answer 1

helium:
- cannot penetrate through paper
- can only go through a few cm of air
- highly ionising

Question 2

beta?

Answer 2

electron:
- cannot penetrate through thick aluminium
- can only go through a few cm of air

Question 3

gamma?

Answer 3

• cannot penetrate through thick lead.
• can go through a few KM of air
• low ionising power

Question 4

activity equation?

Answer 4

number of decays divided by time for decays

Question 5

activity measurement?

Answer 5

Becquerel (Bq)

Question 6

radiation dose?

Answer 6

Sieverts (Sv)

Question 7

contamination?

Answer 7

hazard of contamination is due to the decay of contaminating ions.
type of radiation emitted affects the level of hazard.

Question 8

Isotope?

Answer 8

same number of protons and electrons but different number of neutrons.

Question 9

radioactive contamination?

Answer 9

unwanted presence of materials containing radioactive atoms on other materials

Question 10

Irradiation?

Answer 10

process of exposing an object to nuclear radiation.
The irradiated object does not become radioactive.

Question 11

Ions?

Answer 11

different number of electrons to protons.

Question 12

half-life?

Answer 12

time it takes for half the number of atoms in a sample to decay

Question 13

activity?

Answer 13

rate at which a source of unstable nuclei decays.

Question 14

count-rate?

Answer 14

number of decays recorded per second.

Question 15

solid sphere model?

Answer 15

John Dalton 1803

Question 16

plum pudding model?

Answer 16

J.J Thomson 1904

Question 17

nuclear model?

Answer 17

Ernest Rutherford 1911

Question 18

nuclear fission?

Answer 18

neutron is absorbed by an atom and splits it.
energy is released along with other neutrons.
these neutrons can cause a chain reaction.

Question 18

planetary model?

Answer 18

Niels Bohr 1913

Question 19

nuclear fusion?

Answer 19

2 light nuclei fuse to form a heavier nucleus.
In this process some of the mass may be converted into energy

Question 20

background radiation?

Answer 20

natural- rocks, cosmic rays from space
man-made- nuclear weapons, accidents and medical

Question 21

uses?

Answer 21

. gamma- destroy unwanted tissue (radiotherapy)
. gamma, short half-life- explore internal organs by using tracers
. beta- detects thickness of aluminium foil
. alpha- smoke detectors
. carbon dating

Question 22

hazards?

Answer 22

• can destroy good cells or alter them beyond repair
• the longer the half-life, the more damaging they can do

Question 23

changing energy level?

Answer 23

• absorbing an em wave can cause an electron to go up an energy level
• an electron going down an energy level causes an em wave to be emitted.

Question 24

net decline?

Answer 24

• the number of atoms remaining is 1/2n
• n is the number of half-lives

Question 25

discovering the nucleus?

Answer 25

gold leaf experiment

• plum pudding model= positive alpha particles were aimed at a thin foil of gold.
• according to Thomson’s model, they should pass straight through, but a few bounced off in all directions.
• this lead to the nuclear model with a small nucleus that contained most of the mass and positive charge, with electrons orbiting. (Rutherford)