4 - atomic structure Flashcards

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1
Q

alpha radiation

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

beta raditation

A
  • a neutron will turn into a proton and emit a fast-moving electron
  • no mass
  • few meters in air
  • sheet of aluminion
  • moderately ionising
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3
Q

gamma radiationn

A
  • EM wave
  • long distances in air
  • thick lead or concrete
  • weakly ionising
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4
Q

alpha nuclear equations

A

atomic number -4
mass number -2

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5
Q

beta nuclear equations

A

atomic number 0
mass number +1

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6
Q

gamma nuclear equations

A
  • no change
  • they are just a way of getting rid of excess energy from the nucleus
  • dont have a mass or charge
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7
Q

what is the definition of half life

A

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

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8
Q

how can you measure the radiation of a radioactive substance

A
  • this is entirely random
  • Geiger muller tube and counter
  • ## this records the count rate
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9
Q

what does a short half life mean

A
  • activity falls fast because the nuclei are unstable and decay fast
  • dangerous but then became safe soon after
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10
Q

what does long half life mean

A
  • 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
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11
Q

where does background radiation come from

A
  • unstable isotopes in food / buildings etc
  • cosmic rays in space
  • humans - nuclear waste etc
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12
Q

whats irradiation and how to reduce it and its benefits usage

A
  • 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
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13
Q

whats contamination and how to reduce it

A
  • radioactive atoms get ONTO or INTO. an object which could then decay
  • very dangerous if inside your body
  • gloves / tongs / protective suits
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14
Q

what radiation is dangerous OUTSIDE your body

A
  • beta and gamma bc they can penetrate through your skin
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15
Q

what radiation is dangerous INSIDE your body

A
  • alpha
  • damage a very specific localised area
  • gamma and beta would pass out
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16
Q

risks to raditation

A
  • tissue damage
  • mutate cells - divide uncontrollably - cancer
  • kill cells
17
Q

use of gamma raditation 1

A

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

18
Q

uses of gamma radiation 2

A

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

19
Q

nuclear fission

A
  • nucleus absorbs a neutron then splits unstable atoms into 2 smaller ones and releases 2/3 neutrons
  • chain reaction
  • energy release in gamma rays
20
Q

role of control rods

A
  • 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
21
Q

nuclear fussion

A
  • 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
22
Q

what did john dalton discover

A
  • atoms were solid spheres that made up different elements
23
Q

what did jj thompson discover

A

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

24
Q

what did rutherford discover

A
  • 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
25
Q

what is bohr discover

A
  • electrons orbit the nucleus in fixed shells
26
Q

what did Chadwick discover

A
  • neutrons in the nucleus
27
Q

order of history of model of an atom

A
  1. dalton
  2. thompson
  3. rutherford
  4. bohr
  5. chadiwck
28
Q

activity

A

the rate at which a source of unstable nuclei decays

29
Q

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

A

negative - towards
positive - away

30
Q

what does the strength of the field mean

A
  • stronger the closer to the particle (gets weaker when you go away)
31
Q

what happens when like charges go near each other

A
  • electric field interact
  • strong electrostatic attraction
32
Q

which directions should field lines be drawn

A

positive to negative

33
Q

what is ionisation

A
  • 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)
34
Q

whats the half life or alpha beta and gamma

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