4 - atomic structure

Question 1

alpha radiation

Answer 1

• 2 neutrons 2 protons - helium nucleus
• few cm in air
• sheet of paper
• strongly inising

Question 2

beta raditation

Answer 2

• a neutron will turn into a proton and emit a fast-moving electron
• no mass
• few meters in air
• sheet of aluminion
• moderately ionising

Question 3

gamma radiationn

Answer 3

• EM wave
• long distances in air
• thick lead or concrete
• weakly ionising

Question 4

alpha nuclear equations

Answer 4

atomic number -4
mass number -2

Question 5

beta nuclear equations

Answer 5

atomic number 0
mass number +1

Question 6

gamma nuclear equations

Answer 6

• no change
• they are just a way of getting rid of excess energy from the nucleus
• dont have a mass or charge

Question 7

what is the definition of half life

Answer 7

time taken for the number of radioactive nuclei in an isotope to half

Question 8

how can you measure the radiation of a radioactive substance

Answer 8

• this is entirely random
• Geiger muller tube and counter
• ## this records the count rate

Question 9

what does a short half life mean

Answer 9

• activity falls fast because the nuclei are unstable and decay fast
• dangerous but then became safe soon after

Question 10

what does long half life mean

Answer 10

• activity falls slowly and most nuclei don’t decay for ages
• the source just sits there releasing small amounts of radiation for a long time
• dangerous bc near by places can be exposed to it for millions of years

Question 11

where does background radiation come from

Answer 11

• unstable isotopes in food / buildings etc
• cosmic rays in space
• humans - nuclear waste etc

Question 12

whats irradiation and how to reduce it and its benefits usage

Answer 12

• near or exposed to a radioactive source
• DOESN’T MAKE IT RADIOACTIVE
• reduced by lead lined boxes
• sterilise surgical instruments or destroy cancer cells in patients’ bodies

Question 13

whats contamination and how to reduce it

Answer 13

• radioactive atoms get ONTO or INTO. an object which could then decay
• very dangerous if inside your body
• gloves / tongs / protective suits

Question 14

what radiation is dangerous OUTSIDE your body

Answer 14

• beta and gamma bc they can penetrate through your skin

Question 15

what radiation is dangerous INSIDE your body

Answer 15

• alpha
• damage a very specific localised area
• gamma and beta would pass out

Question 16

risks to raditation

Answer 16

• tissue damage
• mutate cells - divide uncontrollably - cancer
• kill cells

Question 17

use of gamma raditation 1

Answer 17

medical tracers
- injected into ppl and followed around body using an external detector which shows where the strongest reading is coming from
- short half life makes it good

Question 18

uses of gamma radiation 2

Answer 18

radiotherapy
- treating cancer
- direct the correct dosage at the cancer cells and stops them from dividing further

Question 19

nuclear fission

Answer 19

• nucleus absorbs a neutron then splits unstable atoms into 2 smaller ones and releases 2/3 neutrons
• chain reaction
• energy release in gamma rays

Question 20

role of control rods

Answer 20

• used in FISSION
• control the rate of the chain reaction
• lowered and raised inside a nuclear reactor to absorb neutrons and slow down the reaction

Question 21

nuclear fussion

Answer 21

• 2 light nucleui collide and fuse at high speed and join to make alarger heavier nucleus
• releases huge amounts of energy
• temp and pressure must be high
• very hard and ££ to build

Question 22

what did john dalton discover

Answer 22

• atoms were solid spheres that made up different elements

Question 23

what did jj thompson discover

Answer 23

PLUM PUDDING
- Dalton was wrong and atoms weren’t solid spheres
- atoms were ball of positive charge with negative electrons stuck in it

Question 24

what did rutherford discover

Answer 24

• due to plum puding model they thought that firing positive alpha particles through gold sheet they would j pass through BUT…
• some passed through and some deflected back and therfore plum pudding couldnt be right
• new evidence - NUCLEAR MODEL
• positive nucleus in the centre with concentrated mass with a cloud of negative electrons surrounding this nucleus so most of atom is empty space

Question 25

what is bohr discover

Answer 25

- electrons orbit the nucleus in fixed shells

Question 26

what did Chadwick discover

Answer 26

- neutrons in the nucleus

Question 27

order of history of model of an atom

Answer 27

1. dalton 2. thompson 3. rutherford 4. bohr 5. chadiwck

Question 28

activity

Answer 28

the rate at which a source of unstable nuclei decays

Question 29

which directions do you draw field lines for positive and negative particles

Answer 29

negative - towards positive - away

Question 30

what does the strength of the field mean

Answer 30

- stronger the closer to the particle (gets weaker when you go away)

Question 31

what happens when like charges go near each other

Answer 31

- electric field interact - strong electrostatic attraction

Question 32

which directions should field lines be drawn

Answer 32

positive to negative

Question 33

what is ionisation

Answer 33

- strongly charged object in air - air is normally an insulator bc has no charge BUT - a strong electrical field can cause the air to lose electrons and become positive ion - now the air can conduct electricity and this is how sparks travel between objects (through the air)

Question 34

whats the half life or alpha beta and gamma

Answer 34

- alpha - long half life so stays in boyd for ages - beta - short half life so passes out of body