P1 Atomic Structure

Question 1

In standard form, what is the radius of an atom?

Answer 1

1x10*-10

Question 2

How does EM absorption effect electrons?

Answer 2

Move electrons to a higher energy level further from the nucleus

Question 3

How does EM radiation emission effect electrons?

Answer 3

Moved to a lower energy level, nearer to the nucleus

Question 4

Define an isotope

Answer 4

Same number of protons and electrons, different number of neutrons

Question 5

Describe the Plum Pudding Model

Answer 5

• JJ Thompson in 1897

- Atoms are balls of positive charge with electrons bedded in it

Question 6

Describe the Gold Foil Experiment

Answer 6

• 1905, Rutherford and Marsden

- Positive alpha particles fired at a one atom thick sheet of gold foil

Question 7

Why were some alpha particles reflect back during the gold foil experiment?

Answer 7

• repelled by same charge as alpha particles

- repelling particles are heavier than the alpha particle, or alpha particles would’ve passed through

Question 8

What are the conclusions of the Gold Foil Experiment?

Answer 8

• mass of atom concentrated in the centre, positive charge

- surrounded by electrons

Question 9

What did Niels Bohr discover?

Answer 9

Adapted the nuclear model to show electrons orbit at specific distances

Question 10

What did Chadwick discover?

Answer 10

Neutrons, increases knowledge of isotopes

Question 11

Why do atomic nuclei emit radiation?

Answer 11

They are unstable

Question 12

What does type of radiation emitted depend on?

Answer 12

• why the nucleus is unstable

- random and unpredictable

Question 13

Radioactivity is measured in…

Answer 13

Bequerels

1Bq = 1 count / second

Question 14

What is radioactive decay measured with?

Answer 14

Geiger Muller tube

Question 15

Which type of nuclear decay is most ionising?

Answer 15

alpha

Question 16

Which type of nuclear radiation is most penetrating?

Answer 16

Gamma

Question 17

Describe alpha radiation

Answer 17

• two neutrons, two protons (helium nucleus)

- absorbed by and damages living cells

Question 18

Describe beta radiation

Answer 18

• high speed electrons
• ejected from the nucleus when a neutron becomes a proton
• can penetrate through body to inner organs

Question 19

Describe gamma radiation

Answer 19

• em radiation

- passes through living cells without being absorbed or ionising

Question 20

What is another type of nuclear decay?

Answer 20

neutron

Question 21

Define radioactive contamination

Answer 21

unwanted presence of materials containing radioactive atoms on other materials

Question 22

Why is contamination hazardous?

Answer 22

radioactive decay of contaminating atoms

Question 23

What is irradiation?

Answer 23

• exposing an object to nuclear radiation
• deliberate or accidental
• object does not become radioactive

Question 24

How can you prevent unwanted irradiation?

Answer 24

• using sources of lowest activity for shortest time
• wear protective clothing (lead apron)
• don’t handle sources with bare hands

Question 25

Compare hazards of contamination and irradiation (food, area contaminated with alpha)

Answer 25

- food contaminated with alpha would be more hazardous than gamma as alpha is stronger ionising - area contaminated with alpha wouldn’t be dangerous unless it was entered, because it isn’t penetrating gamma would irradiate people nearby as it is highly penetrable

Question 26

What is half life?

Answer 26

A measure of how long it takes for half of the radioactive atoms to decay

Question 27

Explain what is meant by radioactivity being a random event

Answer 27

It is impossible to predict what will decay next

Question 28

Describe isotopes with a short half life

Answer 28

- unstable - emit radiation quickly - exposure is hazardous - aren’t radioactive for long

Question 29

Describe isotopes with long half lives

Answer 29

- more stable - radioactive for longer - emit slowly - exposure is less harmful

Question 30

Describe 4 uses of nuclear radiation

Answer 30

MEDICAL TRACERS - isotope ingested or injected in to body - can be detected from outside as it travels around body MONITORING KIDNEY FUNCTION - isotope used that’ll pass through kidneys - if it builds upon one kidney but not another, one kidney isn’t working efficiently INTESTINE BLOCKAGES - blockage = radioactivity can’t be detected after blockage - damage = radioactive source can be seen passing out of kidneys to other parts of body where it shouldn’t TUMOURS - focussed beam of gamma rays - radioactive iodine for thyroid rumours, gathers in the gland and destroys cells

Question 31

When choosing an isotope for medical use, what should be considered?

Answer 31

half life (needs to be long enough to perform task but not too long that it stays radioactive in patient for a long time) , activity, type of radiation

Question 32

Why are gamma rays best for tracers

Answer 32

- penetrates the body - can be detected from outside - least ionising

Question 33

What are the components of background radiation?

Answer 33

- radon gas - medical (x-rays) - nuclear - cosmic rays - gamma - food 13% man made 87% natural

Question 34

What does someone’s exposure to background radiation depend on?

Answer 34

- location (some places have higher natural background radiation) - occupation (some jobs are exposed to radiation daily)

Question 35

Define nuclear fission and how it occurs

Answer 35

- splitting if a large unstable nucleus (uranium or plutonium) - needs to absorb a neutron (won’t occur on its own) - absorbs a neutron - splits into two equal nuclei - emits: 2/3 neutrons, gamma rays, energy - all products have kinetic energy - chain reaction

Question 36

What are the uses of nuclear fission?

Answer 36

- nuclear reactors ( chain reaction is controlled for constant steady energy release) - explosions in nuclear weapons are uncontrolled chain reactions

Question 37

Describe nuclear fusion

Answer 37

- opposite of fission - two light nuclei join to form a heavier nucleus - some of the mass is converted in to energy which may be emitted as radiation

Question 38

Why does nuclear fusion require high temperatures and pressures?

Answer 38

- overcome electrostatic repulsion | - bring positive nuclei close enough for fusion to occur

Question 39

How is alpha decay represented in nuclear equations?

Answer 39

4 2 He - mass number -4 - atom number -2

Question 40

How is beta decay represented in nuclear equations?

Answer 40

0 -1 e - mass number doesn’t change - atomic number +1