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physics: paper 1 > atomic structure > Flashcards

atomic structure Flashcards

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1
Q

how does radiation in smoke detectors work?

A

-alpha radiation used in smoke detectors
-this ionises the air causing current to flow
-when air has smoke, it absorbs/ stops alpha current is broken = alarm

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2
Q

what is an isotope?

A

-atoms of same element with different number of neutrons

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3
Q

what is radioactive decay?

A

-process of emitting high energy particles or waves from unstable nucleus
-process of emitting radiation

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4
Q

what is irradiation?

A

-process of exposing material to alpha, gamma, or beta radiation
-to sterilise equipment to kill microorganisms
-to sterilise food, makes it last longer

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5
Q

what is contamination?

A

-unwanted radioactive isotope leaking onto material
-much more harm potential, due to continuous radioactive exposure it will produce

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6
Q

changes to atom structure after:
-alpha decay
-beta decay
-gamma decay

A

-alpha: mass no. decreases by 4, atomic no. decreases by 2
new element created
-beta: only change, atomic number +1 (neutron changes to proton and an electron, elec is emitted, proton remains.)

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7
Q

half life:

A

rate at which activity of radioactive material halves.
-time taken for half of nuclei of sample of radioactive isotope to decrease by half

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8
Q

what causes atomic nuclei to become unstable?

A

-because they are too large
-too many or too few neutrons
-imbalance of forces between particles in nucleus

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9
Q

what is activity?

A

rate at which instable nuclei decay

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10
Q

what is count rate?

A

rate at which radioactive emissions detected

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11
Q

what happens when electrons absorb EM radiation?

A

they move to higher energy levels,
-causes atom to be unstable
-to return to original energy level, it moves back down, and emits EM radiation.

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12
Q

when are electrons knocked out of atom?

A

-objects rubbed together, elec removed by friction
-elec can absorb EM radiation to gain enough energy to leave atom
-from chemical reactions

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13
Q

prevention of damage from:
-irradiation
-contamination

A

-IR: lead lined suit, lead absorbs radiation
-CON: air tight suits when working in area that may have radiation leak, prevents atoms getting inside body

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14
Q

what is a dose? how is it measured?

A

-a dose is amount of radiation received by a person
-measured in sieverts (Sv)
-one Sv is very big
normal dose of person per year: 3mSv (0.003 Sv)

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15
Q

what is a bequerel:

A

measurement of amount of radiation emitted by source every second

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16
Q

what is counts per second:

A

number of decays per second????

17
Q

two ways of nuclear fission

A

-spontaneously
fission is unforced and happens by itself (very rare)

-absorbing a neutron
can split a nucleus by making it even less stable

18
Q

name two nuclear fuels

A

uranium-235, plutonium-239

19
Q

steps of nuclear fission

A

-slow moving neutron fired at a large unstable nuclei
-breaks into two smaller nuclei, and two/three neutrons
-energy prod in the form of gamma radiation
-if neutrons slow enough to be absorbed by other large unstable nuclei, chain reaction happens

20
Q

what is the energy prod from fission used for

A

to heat water and prod steam, which can drive turbines connected to an electricity generator

21
Q

pros and cons of nuclear energy

A

PROS
-U and Pu are cheap
-prod a large and steady amount of energy
-clean; doesn’t prod GH gases
CONS
-power plants, very expensive to build
-nucl waste expensive to get rid of
-risk of major disaster

22
Q

process of nuclear fusion

A

-two light nuclei collide at high speeds to prod a heavier nucleus (ex. hydrogen > helium)
-heavier nucleus has less mass than the two separate nuclei, as some mass converted to energy
-creates a lot more energy than fission
-not used to make energy for us as it requires rlly high press & temp
-happens in stars

23
Q

why does fusion only happen at very high temperatures and pressures?

A

to overcome the repulsion of the positively charged nuclei

24
Q

a substance is radioactive when it consists of

A

unstable isotopes that can decay

25
Q

describe an alpha particle

A

-2 protons & 2 neutrons, represented by a helium nucleus
-has charge of 2+
-relatively large, so only travel a few cm and absorbed by paper
-strongly ionising, so can knock electrons off of any atoms they collide w/

26
Q

describe a beta particle

A

-an electron
-no mass
-charge of 1-
-one of the neutrons in the nucleus decays as a proton and electron, proton stays in nucleus and electron emitted at high speed
-tiny so moderately ionising and penetrating

27
Q

describe gamma rays

A

-waves of electromag radiation
-often emitted after alpha or beta radiation
-no mass or charge, so pass right through materials
-not very ionising
-stopped by thick lead/concrete

28
Q

describe neutron radiation

A

if a nucleus has too many neutrons and is unstable, it emits neutrons

29
Q

for a beta decay equation, the atomic mass (top num.) ……….. and the atomic num ……

A

-stays the same
-increases by 1

30
Q

half life can be defined as

A
  • the time taken for the number of radioactive nuclei in a sample to halve
  • the time taken for the number of decays or activity to half
31
Q

what is meant by radioactive activity

A

overall rate of decay of all isotopes in sample

32
Q

what is irradiation

A

the process by which objects are exposed to radiation

33
Q

what makes ionizing radiation dangerous

A
  • can enter living cells and interact with the molecules inside
  • can ionize DNA causing mutations
34
Q

What factors affect the dosage of radiation

A
  • how far from the source you are
  • how long you’re exposed
  • how radioactive the substance is
35
Q

how are medical tracers used in radiation medicine

A

gamma rays are used
patients are made to swallow radioactive isotope
-movement of isotope is traced in the body to see if organs are working properly and are absorbing the right amount of isotope etc.
- only use isotopes with short half lives

36
Q

what type of radiation is used for an internal and external treatment

A

external is gamma
internal is beta

37
Q

Exposure to low levels of radiation over long periods can lead to cancer.

Why is this?

A

Radiation can cause mutations in our DNA…
…which may cause our cells to divide uncontrollably

physics: paper 1 (5 decks)

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