P7

Question 1

whats the radius of an atom?

Answer 1

1 x 10-10

Question 2

most of an atom’s mass is where?

Answer 2

the nucleus

Question 3

what’s the radius of the nucleus?

Answer 3

1/10000 the radius of the atom

Question 4

atomic nuumber

Answer 4

smaller number, shows number of protons

Question 5

mass number

Answer 5

larger number, shows total number of protons and neutrons

Question 6

how can electrons move away from the nucleus

Answer 6

absorption of electromagnetic radiation

Question 7

how can electrons move closer to the nucleus?

Answer 7

emission of electromagnetic radiation

Question 8

isotopes

Answer 8

same number of protons and electrons, different number of neutrons

Question 9

describe alpha

Answer 9

what it is: 2 protons, 2 neutrons (helium nucleus)
absorbed by: skin and paper
range in air: 5cm
ionising power: high
example decay:
219/86 Ra -> 215/84 Po + 4/2 He
causes mass of the nucleus to decrease

Question 10

describe beta

Answer 10

what it is: high speed electron
absorbed by: thin aluminium
range in air: 1m
ionising power: medium
example decay:
14/6 C -> 14/7N + 0/-1 e
doesn’t change the mass of the nucleus, but charge increases

Question 11

describe gamma

Answer 11

what it is: electromagnetic radiation
absorbed by: thick lead
range in air: infinite
ionising power: low
example decay: gamma ray emission does not change the mass or charge of the nucleus

Question 12

describe JJ Thompson’s plum pudding model

Answer 12

• atom is a positive ball, with electrons embedded in it

Question 13

what were the results of the alpha scattering experiment?

Answer 13

• most of the alpha particles passed straight through the foil
• a small number of alpha particles were deflected by large angles (> 4°) as they passed through the foil
• a very small number of alpha particles came straight back off the foil

this led to the discovery of the nucleus

Question 14

what did the nuclear model show?

Answer 14

all the mass and positive charge is concentrated in the centre of the atom- the nucleus

Question 15

What did Bohr do?

Answer 15

added electron orbits to the nuclear model

Question 16

what did Chadwick do 20 years after the Nuclear model?

Answer 16

discovered neutrons

Question 17

radioactive decay is…

Answer 17

random

Question 18

what is half life?

Answer 18

the time it takes for the count rate, activity or number of radioactive nuclei of an isotope to fall to half its initial value

Question 19

Alpha, Beta and Gamma are ___ which means they can remove electrons from atoms. In human cells, this increases risks of ____

Answer 19

ionizing, cancer

Question 20

irradiation

Answer 20

the process of exposing an object to nuclear radiation

Question 21

contamination

Answer 21

the unwanted presence of radioactive substances on other materials

Question 22

where might background radiation come from?

Answer 22

naturally: rocks, cosmic rays
man made: nuclear weapon tests and accidents

Question 23

what could level of background radiation be effected by?

Answer 23

job or location

Question 24

short half-life

Answer 24

• high activity as more radiation is emitted per second
• more dangerous as they can provide a high dose

Question 25

long half life

Answer 25

- emit less radiation per second but stay radioactive for a longer time - some radioactive waste products need to be stored for hundreds of years before they're safe

Question 26

fission

Answer 26

the splitting of a large, unstable nucleus

Question 27

spontaneous fission is ___ as usually the unstable nucleus must _____

Answer 27

rare absorb a neutron

Question 28

the nucleus undergoing fission splits into ____, roughly equal in size, and emits two or three ___ plus ____. ____ is released

Answer 28

two smaller nuclei, neutrons, gamma rays, energy

Question 29

all the fission products have ___, so neutrons could go on to start a ____

Answer 29

kinetic energy, chain reaction

Question 30

T/F the explosion of a nuclear weapon is an example of a controlled chain reaction

Answer 30

F- it's uncontrolled. chain reactions in nuclear reactors are controlled to control energy release

Question 31

fusion

Answer 31

the joining of two light nuclei to form a heavier one. in this process, some mass is converted into energy in the form of radiation

Question 32

how is nuclear radiation used in exploration of internal organs, and state the benefits and risks

Answer 32

radioactive isotopes are taken into the body, and the radiation they emit can be detected outside the body Benefits- doctors can investigate internal organs without surgery Risks- increased danger of developing cancer

Question 33

how is nuclear radiation used in control or destruction of unwanted tissiue, and state the benefits and risks

Answer 33

a beam of high energy radiation (usually gamma) is fired at a tumour Benefits- cancerous tumours can be destroyed or diminished risks- increased danger of developing new cancers