Atomic Structure. 4. Flashcards Preview

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Flashcards in Atomic Structure. 4. Deck (61)
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1
Q

What happened in 1804

A

John Dalton agreed with Democritus that matter was made from atoms that could not be broken and each element was made from a different type of atom.

2
Q

What happened 100 years after 1804

A

J.J Thompson discovered electrons could be removed from atoms.
Thompson said their were elcectrons tuck in a mass of positive charge and mad the “plum pudding model”

3
Q

What happened in 1909- Alpha Scattering

A

Scientists in Rutherfords lab fired a beam of alpha particles to a thin sheet of gold foil - the alpha scattering experiment, from the PP model they expected to pass straight through or only be slightly defected instead most did pass through but some deflected back the reverse direction.

4
Q

What did they realise in The Alpha Scattering Experiment?

A

Nearly all the alpha particles passed through most of the atom was empty space.
Positivley charged nucleus surrounded by a cloud of negative electrons.
Most the mass of an atom must be concentrated in the nucleus.

5
Q

What did Niehls Bohr say?

A

Electrons orbiting the nucleus do so at a distance called energy levels.
Then James Chadwick developed the idea of the neutron whichh explained the imbalance between the atomic and mass numbers.

6
Q

Give the charge of a proton neutron and electron

A
P= +1
N = 0
E = -1
7
Q

Give the mass of a proton neutron and electron

A
P= 1
N = 1
E = 0.0005
8
Q

What happens is electrons gain EM radiation

A

They move to higher energy levels

If they release EM radiation they move to lower energy levels.

9
Q

How does an atom become a positive ion

A

If one or more of the outer electrons leave

10
Q

What is an isotope

A

Atoms with the same number of protons but a different number of neutrons

11
Q

What do unstable isotopes do

A

decay into other elements and give out radiations as they try to become stable. This is called radioactive decay.

12
Q

What is ionsing radiation?

A

knocks of electrons on atoms creating positive ions

13
Q

What is alpha radiation

A

an alpha particle is emmited from a nucleus a charge of +2

14
Q

What is the alpha particles structure

A

two protons and two neutrons a helium nuclei

15
Q

How far do alpha particles penetrate

A

Dont penetrate very far into materials and are stopped quickly

16
Q

What are alpha particles stopped by?

A

A few cm of air

absorbed by a sheet of paper

17
Q

Are alpha particles ionising

A

yes strongly because of their density.

18
Q

What is a beta particle

A

fast moving electron released by the nucleus hae virually no mass and a charge of -1

19
Q

Are beta ionising

A

moderatly

20
Q

How penetrating are beta

A

moderately far into material before colliding and have a range in air of a few metres

21
Q

What is beta stopped by

A

a few metre of air

absorbed by 5mm of aluminum foil

22
Q

What happens when a beta particle is emmited

A

a neutron in the nucleus has changed to a proton

23
Q

What are gamma waves

A

Electromagnetic radiation released by the nucleus

24
Q

How far does gamma penetrate

A

pass through rather than collide with atoms

eventually they hit something and do damge

25
Q

What is gamma absorbed by

A

a few thick sheets of lead

metres of concrete

26
Q

What do nuclear equations show

A

radioactive decay

27
Q

In nuclear equations how is an alpha particle written

A

4 2 he

28
Q

In a nuclear equation how is alpha decay calculated

A

+4 +2

29
Q

How is a beta particle written in a nuclear equation

A

0 -1 e

30
Q

Explain gamma rays in nuclear eqautions

A

gamma rays are a way of given of excess energy from a nucleus so their is no change,

31
Q

Whta is a halflife

A

the time taken for the number radiocative nuclei in an isotope to halve

32
Q

Where do radioactive substances give out radiation

A

nuclie of their atoms

33
Q

Is radioactivity random

A

yes you cant predict exactly which will decay next or when it will decay

34
Q

What is background radiation?

A

low level radiation around us at all times

35
Q

Where does background radiation come from?

A
naturally occuring unstable isotopes 
air
food
building material
rocks under our feet
space- cosmic rays
sun
nuclear waste/explosions
measured in sv
36
Q

What is irradiation

A

exposure to radiation

37
Q

Does irradiation near something make something radioactive

A

no

38
Q

How to keep radioactive substances

A

lead lined box behind barriers with remote controlled arms

39
Q

What happens if unwanted radioactive atoms get on an object

A

it becomes contamintated these contaminating atoms might decay releasing radiation cauing you harm.

40
Q

How to stop being contaminated

A

Gloves and tongs when handling sources

protective suits

41
Q

Which sources are more damaging outside the body and why

A

Beta and Gamma because beoth can penetrate through th body and ionise or organs
Alpha is less as it can only penetrates through a few cm of air

42
Q

Which radiation is most damaging inside the body

A

Alpha as they damage in localised areas Beta is less damaging as its is wider spread and passes through
Gamma is least as it ALL passes through

43
Q

Risks of radiation

A

enters living cells and ionises atoms and molecules inside of them which leads to tissue damage
lower doses tend to minor damge and gives a rise to mutant cells which divdde uncontrolably leading to CANCER
Higher doses tend to kill completley causing radiation sickness leading to HAIR LOSS

44
Q

Explain how a medical tracer is used

A

radioactive isotopes are injected into people and their progress around the body can be followed using a external detector a computer conerts this to show where th highest reading is.

45
Q

How is iodine 123 used as a medical tracer

A

absorbed by the thyroid gland and gives out radiation which can be detected to indicate whether the thyroid gland is taking iodine as it should

46
Q

Which isotope is used as a medical tracer

A

gamma as it passes through without being too ionising

47
Q

How is radiotherapy used to cure cancers

A

gamma rays are directed at the right dose to kill cancer cells without damaging to many healthy cells Beta emmiters can be put next to the tumour

48
Q

Benefits of radioactive materials

A

tracers are used to diagnose conditions and cancer risk is small

49
Q

Risks of using radiactivity

A

prolonged exposure can damage cells but then end result is cancer free it outweighed by the benefit

50
Q

What is nuclear fission?

A

Splitting a large unstable nucleus

nuclear reaction which releases energy from large and unstable atoms by splitting them into smaller atoms

51
Q

When will the nucleus split in fission

A

when it has absorbed a neutron

52
Q

In fission when an atom splits what is the product

A

two lighter elements that have some energy in there kinetic stores
2 or 3 neutrons are also released when fission takes place if any neutrons are slow they can be absorbed by another nucleus causing more fission which is called a CHAIN REACTION

53
Q

what happens to the energy not transferred to the kinetic enrgy stores of the product?

A

carried away by gamma rays and in th ekinetic energy stores of the free neutrons can be used to heat water turbines and generators

54
Q

How to change the amount of energy prodiced by fission?

A

change how quickly the chain reactions are by control rods which are lowered and raised by a nuclear reactor to absorb neutrons slow reaction and control energy used

55
Q

What is nuclear fusion

A

two nuclei collide at high speed and fuse to create a larger heavier nucleus ex
hydrogen nuclei can fuse to become a helium nucleus

56
Q

What releases more enrgy fission or fusion

A

fusion

57
Q

is fussion used

A

no temp and pressure needed is to high that is it is too expensive

58
Q

What does a heavier nucleus made by fusion show

A

it doesnt have as much mass as the two sperate nuclei did some of the mass of the lighter nuclei is converted as energy then released as radiation

59
Q

State how a nuclear power station works

A

reactor contain fuel rods
nuclear fission occur in the uranium rods
energy released used to heat water in the boiler turinging it to steam
steam turns turbines
turbine turns generator
generator creates electrical energy

60
Q

Disadvantages of nuclear power stations

A
long time to build
decomsioning is high
nuclear explosion
hard to secure safley
expensive
61
Q

State why urainum is better than coal

A

it produces pollutant gases which harm the environement