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Physics > Atomic Structure > Flashcards

Atomic Structure Flashcards

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1
Q

Structure of an atom

A

A positively charged nucleus composed of both protons and neutrons surrounded by negatively charged electrons

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2
Q

How can electron arrangements change

A
  • With the absorptions of electromagnetic radiation -> move further away from the nucleus
  • By the emission of electromagnetic radiation -> move closer to the nucleus
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3
Q

Mass number

A

Total number of protons and neutrons in an atom

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4
Q

Atomic number

A

Number of protons in an atom

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5
Q

Isotope

A

Elements with the same number of protons but different number of neutrons

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6
Q

Plum pudding model

A

Suggested that the atom is a ball of positive charge with negative electrons embedded in it

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7
Q

Alpha particle scattering experiment results

A
  • the mass of an atom was concentrated at the centre of
  • there was a positively charged nucleus
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8
Q

Nuclear model (Neils Bohr)

A

Suggested electrons orbit the nucleus at specific distances

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9
Q

James Chadwick

A

Discovered neutrons

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10
Q

Radioactive decay

A

When atomic nuclei are unstable and given out radiation as it changes to become more stable

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11
Q

Activity (Bq)

A
  • the rate at which a source of unstable nuceli decays
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12
Q

Count rate

A

The number of decays recorded each second

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13
Q

Alpha particle

A
  • consists of 2 neutrons and 2 protons (the same as a He nucleus)
  • highest ionising power
  • travels few cms in air
  • stopped by a sheet of paper
  • +2 charge
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14
Q

Beta particle

A
  • a high speed neutron ejected from the nucleus turns into a proton and an electron -> the electron that escapes is the beta radiation
  • high ionising power
  • travels ~1m in air
  • stopped by aluminium
  • -1 charge
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15
Q

Gamma ray

A
  • high energy EM wave emitted by the nucleus
  • low ionising power
  • travels unlimited in air
  • stopped by lead or concrete
  • 0 charge
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16
Q

Name the types of nuclear radiation

A
  • alpha
  • beta
  • gamma
  • a neutron
17
Q

Half-life

A

The time it takes for the number of nuclei of an radioactive isotope in a sample to halve

OR the time it takes for the activity from a sample containing a radioactive isotope to half

18
Q

Radioactive contamination

A
  • the presence of unwanted materials containing radioactive atoms
19
Q

Irradiation

A
  • the process of exposing an object to nuclear radiation
20
Q

Protection against irradiation and contamination

A
  • maintaining distance from the radiation source
  • limiting time near the source
  • shielding from the radiation

(Contamination is harder to remove)

21
Q

Where does background radiation come from

A
  • natural sources -> rocks and cosmic rays from space
  • man-made sources -> fallout from nuclear weapons and nuclear accidents
22
Q

What is radiation dose measured in

A

Sieverts (Sv)

1000mSv = 1Sv

23
Q

Nuclear radiation use for the exploration of internal organs

A

Gamma emitting tracers are injected -> gamma cameras can then create an image showing where the tracer has gone

-> the half-life of the tracer must’ve be short enough so that most of the nuclei decay shortly after the image is taken to limit patients radiation dose

24
Q

Nuclear radiation used for the control or destruction of unwanted tissue

A
  1. Narrow beams of gamma radiation can be focused in tumour cells to destroy them (gamma used as it can penetrate from outside the body)
  2. Beta or gamma emitting radiation can be surgically placed inside tumours -> their half-lives must’ve be long enough to be effective, but short enough that it doesn’t continue to irradiate the patient after treatment
25
Q

Nuclear fission

A

The splitting of a large unstable nuclei into 2 smaller ones

-> it occurs when the unstable nucleus absorbs a neutron
-> the nucleus splits into 2 smaller nuclei and emits 2-3 neutrons (go on to form a chain reaction) plus gamma radiation

26
Q

How is the chain reaction in nuclear fission controlled in a nuclear reactor

A

There are control rods that control the rate that neutrons are absorbed

27
Q

What are nuclear explosion

A

Uncontrolled chain reactions

28
Q

Nuclear fusion

A

The joining of 2 light nuclei to make a heavier one

-> in the process some of the mass is converted to energy and transferred as radiation

29
Q

In what order were the subatomic particles discovered

A
  • electrons
  • protons
  • neutrons
30
Q

How alpha radiations is used in smoke alarms

A
31
Q

How does beta detect thickness of paper

A
32
Q

How is gamma used for radiotherapy

A
33
Q

How is gamma used for sterilisation

A

Kills microbes

34
Q

Is the total mass of particles in fission bigger afterwards or before

A

Before because mass has been converted into energy

35
Q

What is fission induced by

A

A neutron absorbing a neutron which makes it more unstable

36
Q

How are fission reactors controlled

A

Using control rods which are raised or lowered to stop neutrons being released which affects the rate of reaction

37
Q

Why does fusion have to take place at high temperatures and pressures

A

To be able to overcome the repelling nuclei with the same charge

38
Q

How and why do sparks occur

A
  • When there is a difference between the positive and negative charge of two objects, there is a potential difference between the two objects.
  • This potential difference causes a rapid transfer of charge.
  • Energy is stored in an electrostatic store and a spark is produced.
39
Q

How does static electricity lead to sparking

A
  • Eventually, the charge difference between the earth and charged surface gets so big that electrons will jump from the charged surface to the earth
  • As the electrons jump, we will be able to see a spark

Physics (10 decks)

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