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Physics > Atomic structure > Flashcards

Atomic structure Flashcards

1
Q

What did Rutherford’s alpha scattering experiment prove?

A
  1. Straight through particles = empty space in the atom
  2. Slightly deflected = the alpha particles hit positively charged particles (protons)
  3. Directly backwards = positive mass was concentrated in a tiny nucleus
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2
Q

What was Niels Bohr’s discovery

A

Electrons orbit the nucleus at certain distances called energy levels

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3
Q

What was James Chadwick’s discoveries

A

Neutrons to explain the imbalance between atomic and mass numbers

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4
Q

Features of a proton

A

Mass = 1
Charge = +1

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5
Q

Features of a neutron

A

Mass = 1
Charge = 0

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6
Q

Features of an electron

A

Mass = 0
Charge = -1

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7
Q

Why does an atom have no overall charge

A

Protons always equal electrons

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8
Q

How can energy levels move in an atom

A

Absorbing or losing EM radiation

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9
Q

What is an isotope

A

An atom with the regular number of protons (same charge) but different amount of neutrons (different mass)

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10
Q

How many isotopes of an element are stable

A

1 or 2

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11
Q

How do unstable isotopes attempt to become stable

A

Decay into other elements and give out radiation to try and become stable

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12
Q

What is ionizing radiation

A

Radiation which knocks electrons off an atom, creatin an ion

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13
Q

Features of an alpha particle

A
  1. Helium nucleus (2 protons, 2 neutrons)
  2. Not very penetrating (stopped by a few cm of air and absorbed by a sheet of paper)
  3. Strongly ionizing
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14
Q

Features of a beta particle

A
  1. Fast moving electron
  2. Moderately penetrating (can travel a few metres of air, absorbed by a sheet of aluminium)
  3. For every beta particle emitted, a neutron becomes a proton
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15
Q

Features of a gamma ray

A
  1. Waves of electromagnetic radiation
  2. Very penetrating (absorbed by thick sheets of lead/ concrete)
  3. Weakly ionizing, as they pass straight through
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16
Q

Nuclear equation for an alpha particle

A
    • 4 from the mass
  2. -2 from the atomic number
    • a helium nucleus
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17
Q

Nuclear equation for a beta particle

A
  1. +1 to the atomic number
    • a 0 weight, -1 atomic number electron
18
Q

How is radiation measured

A

Geiger Muller tube and counter

19
Q

What is half life

A

The time taken for the amount of radioactive nuclei in an isotope to halve

20
Q

What is radioactivity measured in

A

becquerels

21
Q

What does a short half life mean

A
  1. Activity falls quickly
  2. Nuclei are very unstable and decay quickly
22
Q

What does a long half life mean

A
  1. Activity falls slowly
  2. Most nuclei don’t decay for a long time
23
Q

How is half life shown on a graph

A

An exponential curve

24
Q

What is background radiation

A

Low level that is around us all the time due to the unstable isotopes in objects all around us

25
Q

Why do cosmic rays from the Sun not affect humans

A

The Earth’s atmosphere block the radiation

26
Q

What does irradiated mean?

A

An object exposed to radiation

26
Q

3 sources of background radiation

A
  1. Sun
  2. Naturally occurring unstable isotopes
  3. Human activity
27
Q

3 ways to avoid irradiation?

A
  1. Lead lined boxes
  2. Standing behind barriers
  3. Remote controlled arms
28
Q

2 ways to avoid contamination?

A
  1. Gloves
  2. Tongs
29
Q

Which radiation types are most dangerous outside the body

A

Beta and gamma can penetrate skin and damage organs

30
Q

Which radiation type is most dangerous inside the body

A

Alpha ionize a very localised area

31
Q

Difference between irradiation and contamination

A

Irradiation is being exposed to a radioactive source, contamination is radiation getting inside or onto an object

32
Q

How can radiation damage the body?

A

Radiation can enter living cells and ionize atoms and molecules within them and cause mutant cells which divide uncontrollably (cancer)

33
Q

How are gamma rays used in medicine

A
  1. Iodine 123 can detect if the thyroid is taking in iodine as it should
  2. Gamma rays can be directed carefully at tumours to kill cancer cells without damaging normal cells
34
Q

Benefits of radiation treatment

A
  1. Tracers can detect life threatening illnesses
  2. Risk of cancer from one is very low
  3. Cancer can be cleared
35
Q

Risks of radiation treatment

A

Side effects

36
Q

What is fission

A

Releasing energy from large, unstable nuclei by splitting them into smaller, lighter elements

37
Q

Explain fission

A
  1. A nucleus absorbs a neutron
  2. The nuclei split to form to similarly sized elements with some energy in their kinetic energy stores
  3. Two or three nuclei are also released which, if moving slow enough, can be absorbed by another nuclei starting a chain reaction
  4. Energy not in kinetic energy stores is released in gamma rays
38
Q

What can fission be used for

A

Remaining free neutrons and other decay products can heat water to make steam to turn turbines and generators

38
Q

How is fission controlled

A

Control rods in nuclear generators can be lowered and raised to absorb neutrons, slow down the reaction and control energy being released

39
Q

Explain fusion

A
  1. Two light nuclei move towards each other at high speed to create a larger, heavier nucleus
  2. The heavier nucleus does not have as much mass as the two lighter nuclei as some is converted into energy (gamma rays)
    3, Lots of energy is released

Physics (8 decks)

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