AQA GCSE physics: Atomic structure

What did JJ Thomson discover?

electrons

What did JJ Thompson's modle prove?

Atoms weren't the fundamentals of elements and that atoms are neutral

Plum Pudding Model

What was the alpha scattering experiment?

Rutherford fired alpha particles at a surface expecting them to pass right throug, alot did but some refracted and some didn't pass through at all

Why did the alpha particles refract?

The alpha particles that got close to the nucleus refracted due to them being a helium atom

Why did some alpha particles bounce back the way they had came in the alpha scattering experiment?

They hit the nucleus and couldn't penetrate

Alpha scattering experiment

What was Rutherford's model?

Nuclear model

What did Rutherford's model prove?

Their are also positively charged protons and electronically charged neutrons that make up the nucleus

Rutherford model

Elements

What is the atomic number?

number of protons

What is the mass number?

Number of protons and neutrons

What are isotopes?

atoms with the same number of protons but different number of neutrons

What makes an atom stable?

A full outer layer of electrons

What makes an atom radioactive?

Atoms with unstable nuclei are said to be radioactive. Sooner or later, they break down and eject energetic particles and emit electromagnetic radiation.

What is a half-life?

length of time required for the radioactive atoms in a sample to decay by 50%

How do you calculate half-life?

A=A^o(0.5)^t/h

volume of distribution and clearance

What is half-life measured in?

Becquerels (Bq)

What is nuclear fission?

a process that releases energy by splitting nuclei apart

How does nuclear fission work?

uranium atoms split by shooting neutrons at them

positives - high energy yield
negatives - produces radioactive waste

How is fission used?

The nuclear reaction releases energy in the form of heat which is used in nuclear power stations to boil the water which is then used to drive a turbine with the steam

Fission in use in nuclear power stations

How is fission used in nuclear power stations?

Chain reactions are started and neutron is fired from uranium into another uranium atom

Nuclear fission begins

Heat given off is used to boil water

Steam produced is used to turns a turbine

This turns a generator

This produces electricity

What are the advantages of using nuclear fission to produce electricity?

Cheap to run
Conserves energy
No CO2 emissions
Less transport needed
Safe under normal conditions

What are the disadvantages of using nuclear fission to produce electricity?

Expensive to build
Expensive to decomission
Produces radioactive waste
Carcinogenic
Non-renewable
Risk of nuclear disaster

What is alpha radiation?

helium nucleus: 2 protons and 2 neutrons

What is beta radiation?

The product of the decomposition of a neutron and is composed of high energy high-speed electrons

What is gamma radiation?

an electromagnetic wave

What equation represents alpha radiation?

What equation represents beta radiation?

0/-1

What is alpha radiation stopped by?

5cm of air, paper, skin etc.

What is beta radiation stopped by?

A few mm of aluminium

What is gamma radiation stopped by?

Thick lead absorbs most but not all of the radiation

Is alpha affected by magnetic or electric fields?

Deflected by both and it deflects upwards due to positive charge

Is beta affected by magnetic or electric fields?

Deflected by both and deflects downwards due to negative charge

Is gamma affected by magnetic or electric fields?

No as it travels in waves and has no charge

How ionising and pentetrating are alpha particles?

Very ionising but not very penetrating

How ionising and pentetrating are beta particles?

Quite ionising and penetrating

How ionising and pentetrating are gamma particles?

Not very ionising but most penetrating

Alpha particle

Beta particle

Gamma wave

0/0

What is carbon dating?

a way to measure the age of dead organisms by comparing the amount of carbon-14 from the dead organism to a living one

Uses beta radiation as all living things take in carbon-14

What are tracers?

radioactive isotopes that can be followed through the steps of a chemical reaction or industrial process to test for blockage

If there is a blockage, they build up and can be detected

Uses gamma radiation as they have shortest half life and least ionising

How is radiation used in smoke alarms?

There is a gap the supplies alpha particles through it, if there is smoke, the supply is cut off and the alarm sounds

Alpha particles are used a sthey ahve a long half life an dleats penetrating hence can't pass through the smoke

How is radiation used as a metal thickness tracker?

Beta particles are fired at alluminium an dif they can no longer be detected, the metal is too thick

Beta particles ara used as they are stopped by thick alluminium

What is nuclear fusion?

the process of combining lightweight nuclei to make heavier nuclei