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Physics > P7 > Flashcards

P7 Flashcards

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1
Q

whats the radius of an atom?

A

1 x 10-10

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2
Q

most of an atom’s mass is where?

A

the nucleus

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3
Q

what’s the radius of the nucleus?

A

1/10000 the radius of the atom

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4
Q

atomic nuumber

A

smaller number, shows number of protons

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5
Q

mass number

A

larger number, shows total number of protons and neutrons

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6
Q

how can electrons move away from the nucleus

A

absorption of electromagnetic radiation

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7
Q

how can electrons move closer to the nucleus?

A

emission of electromagnetic radiation

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8
Q

isotopes

A

same number of protons and electrons, different number of neutrons

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9
Q

describe alpha

A

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

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10
Q

describe beta

A

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

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11
Q

describe gamma

A

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

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12
Q

describe JJ Thompson’s plum pudding model

A
  • atom is a positive ball, with electrons embedded in it
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13
Q

what were the results of the alpha scattering experiment?

A
  • 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

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14
Q

what did the nuclear model show?

A

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

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15
Q

What did Bohr do?

A

added electron orbits to the nuclear model

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16
Q

what did Chadwick do 20 years after the Nuclear model?

A

discovered neutrons

17
Q

radioactive decay is…

A

random

18
Q

what is half life?

A

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

19
Q

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

A

ionizing, cancer

20
Q

irradiation

A

the process of exposing an object to nuclear radiation

21
Q

contamination

A

the unwanted presence of radioactive substances on other materials

22
Q

where might background radiation come from?

A

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

23
Q

what could level of background radiation be effected by?

A

job or location

24
Q

short half-life

A
  • high activity as more radiation is emitted per second
  • more dangerous as they can provide a high dose
25
Q

long half life

A
  • 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
26
Q

fission

A

the splitting of a large, unstable nucleus

27
Q

spontaneous fission is ___ as usually the unstable nucleus must _____

A

rare
absorb a neutron

28
Q

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

A

two smaller nuclei, neutrons, gamma rays, energy

29
Q

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

A

kinetic energy, chain reaction

30
Q

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

A

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

31
Q

fusion

A

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

32
Q

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

A

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

33
Q

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

A

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

Physics (7 decks)

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