4 - atomic structure Flashcards
alpha radiation
- 2 neutrons 2 protons - helium nucleus
- few cm in air
- sheet of paper
- strongly inising
beta raditation
- a neutron will turn into a proton and emit a fast-moving electron
- no mass
- few meters in air
- sheet of aluminion
- moderately ionising
gamma radiationn
- EM wave
- long distances in air
- thick lead or concrete
- weakly ionising
alpha nuclear equations
atomic number -4
mass number -2
beta nuclear equations
atomic number 0
mass number +1
gamma nuclear equations
- no change
- they are just a way of getting rid of excess energy from the nucleus
- dont have a mass or charge
what is the definition of half life
time taken for the number of radioactive nuclei in an isotope to half
how can you measure the radiation of a radioactive substance
- this is entirely random
- Geiger muller tube and counter
- ## this records the count rate
what does a short half life mean
- activity falls fast because the nuclei are unstable and decay fast
- dangerous but then became safe soon after
what does long half life mean
- 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
where does background radiation come from
- unstable isotopes in food / buildings etc
- cosmic rays in space
- humans - nuclear waste etc
whats irradiation and how to reduce it and its benefits usage
- 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
whats contamination and how to reduce it
- radioactive atoms get ONTO or INTO. an object which could then decay
- very dangerous if inside your body
- gloves / tongs / protective suits
what radiation is dangerous OUTSIDE your body
- beta and gamma bc they can penetrate through your skin
what radiation is dangerous INSIDE your body
- alpha
- damage a very specific localised area
- gamma and beta would pass out
risks to raditation
- tissue damage
- mutate cells - divide uncontrollably - cancer
- kill cells
use of gamma raditation 1
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
uses of gamma radiation 2
radiotherapy
- treating cancer
- direct the correct dosage at the cancer cells and stops them from dividing further
nuclear fission
- nucleus absorbs a neutron then splits unstable atoms into 2 smaller ones and releases 2/3 neutrons
- chain reaction
- energy release in gamma rays
role of control rods
- 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
nuclear fussion
- 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
what did john dalton discover
- atoms were solid spheres that made up different elements
what did jj thompson discover
PLUM PUDDING
- Dalton was wrong and atoms weren’t solid spheres
- atoms were ball of positive charge with negative electrons stuck in it
what did rutherford discover
- 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
what is bohr discover
- electrons orbit the nucleus in fixed shells
what did Chadwick discover
- neutrons in the nucleus
order of history of model of an atom
- dalton
- thompson
- rutherford
- bohr
- chadiwck
activity
the rate at which a source of unstable nuclei decays
which directions do you draw field lines for positive and negative particles
negative - towards
positive - away
what does the strength of the field mean
- stronger the closer to the particle (gets weaker when you go away)
what happens when like charges go near each other
- electric field interact
- strong electrostatic attraction
which directions should field lines be drawn
positive to negative
what is ionisation
- 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)
whats the half life or alpha beta and gamma
- alpha - long half life so stays in boyd for ages
- beta - short half life so passes out of body
