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GCSE Physics > Unit 4 - Atomic Structure > Flashcards

Unit 4 - Atomic Structure Flashcards

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1
Q

State why the nuclei of certain atoms/isotopes are unstable

A

The nuclei of certain atoms/isotopes are unstable due to the number of protons and nucleus in the nucleus of an atom

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2
Q

What do radioactive isotopes do

Some isotopes are radioactive. What does this mean.

A

(it means that)Their nuclei decay and release radiation

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3
Q

What is radioactive decay

A

Radioactive decay is the random process of a radioactive substance giving out radiation from the nuclei of its atoms.

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4
Q

Some isotopes/certain atoms have an _______

A

Some isotopes/certain atoms have an unstable nucleus

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5
Q

What must the nuclei of atoms do to become stable

A

To become stable the nucleus must release radiation (decay - radioactive decay) in the form of a particle or as an electromagnetic wave

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6
Q

Radioactive decay is a totally ______ process

A

Radioactive decay is a totally random process

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7
Q

What is activity

A

The activity is the rate at which a source of unstable nuclei decay.

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8
Q

Activity is measured in _____

units of activity

A

Activity is measured in becquerel (Bq)

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9
Q

Activity is measured in _____

A

Activity is measured in becquerel (Bq)

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10
Q

1 Bq =

A

1Bq = 1 decay per second

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11
Q

What is a Geiger-Muller tube used for

A

To measure the activity of a radioactive source we can use a Geiger-Muller tube

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12
Q

What is count rate

A

Count-rate is the number of decays recorded each second by a detector (such as: Geiger-Muller tube)

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13
Q

How is count rate different to activity

A

It must be remembered that the count recorded by the G-M tube will be caused by the radiation from the source plus that due to background radiation.

The activity is the rate at which a source of unstable nuclei decay.

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14
Q

When it comes to atoms emitting radiation what can and cant we predict

A

We cannot predict when an atom will give out radiation
We can predict what percentage of the atoms will give out radiation

can’t predict which nucleus will
decay next
or
can’t predict when a (particular)
nucleus will decay

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15
Q

What is ionising radiation

A

Radiation that has enough energy to knock of electrons off atoms (to become an ion)

Radiation hits an atom and caused the atom to become an ion - loses/gains electrons

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16
Q

When it comes to radiation what is random and what can we predict

A

The process of emitting radiation is completely random

We can predict what percentage of the atoms will give out radiation

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17
Q

Who discovered the electron

A

J.J. Thomson

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18
Q

Who developed the plum pudding model (of the atom)

A

J.J. Thomson

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19
Q

describe the the alpha scattering experiment

A

A beam of alpha particles was aimed at very thin gold foil and their passage through the foil was detected.

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20
Q

why was the alpha scattering experiment done

A

Scientists (Rutherford) wanted to know if the plum pudding model was correct, and to find this out they carried out an experiment

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21
Q

What did J.J. Thomson do

A

He discovered the electron, and he then developed the Plum Pudding Model (of the atom)

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22
Q

The discovery of the electron led to what?

A

The discovery of the electron led to the plum pudding model of the
atom

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23
Q

Describe the plum pudding model

A

The Plum Pudding Model is a ball of positively charged matter containing negative electrons

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24
Q

Draw the plum pudding model

A

https://images.twinkl.co.uk/tr/image/upload/t_illustration/illustation/Plum-Pudding-Model—Science-Diagram-KS4.png

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25
Q

Scientists knew that atoms contained electrons and that electrons had a negative charge
They also knew that an atom was electrically neutral overall
What did this allow the scientists to deduce about the pudding part of the atom

A

The pudding part of the atom had a positive charge - it has an equal amount of positive charge as there are negative charge

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26
Q

Who did the Alpha-particle scattering experiment

A

Ernest Rutherford

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27
Q

What model of atom was the plum pudding model replaced with

A

The nuclear model

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28
Q

State the results obtained by Mr Rutherford for the Alpha-particle scattering experiment

A

Most alpha particles went straight through the gold foil without causing damage

Some alpha particles ere deflected through small angles

About 1 in 8000 of the alpha particles were reflected straight back

29
Q

Using the nuclear model of the atom explain why the alpha particles went in those directions

A

Most of the atom is empty space therefore the alpha particles could pass through

The atom contained a nucleus which was positively charged which deflected the alpha particles

Most of the mass of the atom was concentrated in the positively charged nucleus, which caused the alpha particles to be reflected straight back

30
Q

Using the nuclear model, Rutherford devised an equation to predict the proportion of alpha particles that would be deflected though various angles

The results of the experiment were the same as the predictions made by Rutherford

What was the importance of the experimental results and the predictions being the same

A

The experimental results proved the predictions were correct

31
Q

Why did the Alpha particle scattering experiment lead to a new model of the atom, called the nuclear model, replacing the ‘plum pudding’ model

A

The results of the experiment could not be explained by the plum pudding model therefore a new model had to be produced

32
Q

the difference between the plum pudding model of the atom
and the nuclear model of the atom

A

The Plum Pudding Model is a ball of positively charged matter containing negative electrons

the nuclear atom there is a tiny, dense positively charged nucleus at the centre, where most of the mass is concentrated. A cloud of negative electrons surrounds this nucleus - so most of the atom is empty space

___________
while the nuclear model has electrons that are orbiting around this nucleus (centre of the atom), which contains very dense positively charged protons

33
Q

When was:
the proton, neutron discovered

A

Proton - 1917
Neutron - 1932

34
Q

What were atoms thought to be before the discovery of the electorn

A

Before the discovery of the electron, atoms were thought to be tiny
spheres that could not be divided.

35
Q

Describe how the proton and neutron were discovered

A

Later experiments led to the idea that the positive charge of any
nucleus could be subdivided into a whole number of smaller
particles, each particle having the same amount of positive charge.
The name proton was given to these particles.

The experimental work of
James Chadwick provided the evidence
to show the existence of neutrons within the nucleus.

36
Q

What did Niels Bohr say in 1913

A

In 1913, Niels Bohr said that electrons orbit at different (/specific) distances from the nucleus

Bohr’s work agreed with the results of experiments by other scientists (so it was accepted)

These orbits are called energy levels/shells

37
Q

What is the size of radius of an atom

A

Atoms are very small, having a radius of about 1 × 10-10 metres.

38
Q

Describe the structure of an atom

A

The atom has a positively charged nucleus.

The nucleus has positively charged protons and neutrons which have got no charge.

The nucleus is surrounded by negatively charged electrons

The electrons are arranged at different distances from the nucleus
(different energy levels).

39
Q

What is the size of the radius of an nucleus

A

The radius of a nucleus is less than 1/10 000 of the radius of an atom

40
Q

How are the electrons in the nucleus arranged

A

The electrons are arranged at different distances from the nucleus
(different energy levels).

41
Q

How might electron arrangement change when radiation is absorbed or emitted

A

If the atom absorbs
(electromagnetic) radiation an electron can move from a lower energy level to a higher energy level (the atom can now emit electromagnetic radiation and the electron returns back to the lower energy level)

If the atom emits radiation an electron can move from a higher energy level to a lower energy level

42
Q

how is an alpha particle different from a helium atom

A

An alpha particle has 2 protons and 2 neutrons whereas a helium atom has 2 protons, 2 neutrons and 2 electrons.

43
Q

State the four types of radiation

A

Alpha
Beta
Gamma
Neutron

44
Q

Types of nuclear radiation

A

An alpha particle (α)
A beta particle (β)
A gamma ray (γ)
A neutron (n)

https://banner2.cleanpng.com/20180723/qby/kisspng-gamma-ray-symbol-ionizing-radiation-5b5563c7659891.2656795115323227594162.jpg

45
Q

What is an alpha particle

A

A particle which consists of two protons and two neutrons (IT IS THE SAME AS A HELIUM NUCLEUS)

46
Q

State the charge of an alpha particle

A

+2

47
Q

penetrating power

A

Tells us what type of material is required to stop each form of radiation

48
Q

what is ionising power

A

When radiation collides with atoms, that can cause the atoms to lose electrons and form ions

Very strongly ionising means that the radiation can produce a lot of ions when they collide with a material

49
Q

What can stop alpha radiation (penetrating power)

A

Alpha particles can be stopped by

5cm of air
A single sheet of paper
Top layer of skin

50
Q

Alpha particle’s range in air

A

Alpha particles are large. They can travel around 5cm in air before they collide with air particles and stop

51
Q

Describe the ionisation ability (ionising power) of an alpha particle

A

Very Strongly ionising

52
Q

Are alpha particles affected by electric and magnetic fields

A

Yes

53
Q

How is an atom neutral

A

An atom contains the same number of positively charged protons as negatively charged electrons

(the negative charges on the electrons cancel out the positive charges on the protons, making the overall atom neutral)

54
Q

Is an alpha particle dangerous

A

Outside the body - No
Inside the body - very dangerous

55
Q

What is a beta particle

A

A beta particle is a high speed electron ejected from the nucleus as a neutron turns into a proton

A beta particle is an electron that originates from the nucleus

56
Q

Beta particle’s range in air

A

Beta particles range in air about 1m before stopping

57
Q

How is a beta particle formed (since nucleus of atoms do not contain electrons)

A

A beta particle is formed inside the nucleus when a neutron changes into a proton and an electron

The electron is ejected from the nucleus. This electron is called a beta particle

58
Q

What stops a beta particle (penetrating power)

A

3mm of Aluminium

harder to stop than alpha particle

59
Q

State the ionisation ability of a beta particle

A

moderately/quite strongly ionising (not as ionising as alpha particles - since they are smaller)

___________

Very weak (since it is smaller)

60
Q

Are beta particles affected by electric and magnetic fields

A

Yes (any charged particle is affected)

61
Q

Are beta particles dangerous

A

Yes - but it is more dangerous outside the body than inside the body

62
Q

What is a gamma ray

A

A gamma ray is a very high energy electromagnetic wave, originating from the nucleus

63
Q

Gama radiation range in air

A

Gamma radiaiton travels several metres in air before stopping

(unlimited - spreads out in air without being absorbed - aqa textbook)

64
Q

What can stop a gamma ray (penetrating power)

A

Nothing
But, thick lead and concrete can reduce its intensity
_______________
several centimetres of lead
metres of concrete (more than 1m thick)

65
Q

Ionisation ability of a gamma ray (ionising power)

A

Very weak

weakly ionising

66
Q

Is it affected by electric and magnetic fields

A

No

67
Q

Are gamma rays dangerous

A

Yes but it is more dangerous outside the body than inside the body

68
Q

Draw the symbol for an alpha particle, beta particle and a gamma ray

A

α - alpha
β - beta
https://upload.wikimedia.org/wikipedia/commons/thumb/b/b2/Latin_letter_small_capital_Gamma.svg/2185px-Latin_letter_small_capital_Gamma.svg.png - gamma

GCSE Physics (30 decks)

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