Atomic + Nuclear

Plum pudding model

Made by JJ Tompson and Lord Rutherford. Electrons dotted throughout the atom like currents in a bun

Rutherfords evidence of neculi

. Fired positively charged alpha particles at thin gold foil

. Some were deflected through large angles

. Repelled positive alpha particles so the nucleus had to be positively charged

Atomic mass

Number of protons + neutrons (A)

Atomic number

Number of Protons (Z)

Isotope

Atom with the same number of protons but with different neutrons

Radioactive decay

The neculi in some atoms are radioactive as they contain unstable combinations of neutrons and protons. Emitting radiation makes them more stable

Ionising Radiation

the neculi of some atoms emit radiation known as ionising radiation because it passes through matter which causes atoms to turn into ions. There is a chance that the living cells can become cancerous

Alpha particles

. Helium with 2 protons and neutrons

. Positively charged

. reflects magnetic fields

. poor penetration power

. strongest ionising power

Beta particles

. Fast moving electron

. Relative atomic mass of 0

. negativity charged

. reflects magnetic field

. faster than alpha particles

. more penetration power

. ionising power between alpha and gamma

Gamma rays

. High energy wave ( no mass )

. high penetration power

. weak ionising power

. magnetic field = no affect

Background Radiation

. Carbon 14 isotopes can be radioactive

. Radioactive elements in food

. Certain rocks contain uranium

. Radiation from space

Detecting radiation

Gieger muller tube

Dangers of radiation

. Cell + DNA damage

. burns

. radiation sickness

Minimising damage

. minimal exposure

.use tools

.wear protective clothing

.always store substances in lead box

Uses of alpha radiation

. Smoke detectors

Uses of beta radiation

. tracking / monitoring thickness

. medical imaging

. dyes to identify areas of the heart

Uses of gamma radiation

. kill cancers

. sterilise equipment

. preserving foods

. x ray machines

. security scanners

Half Life

Time taken for radioactive activity to fall by half

unit - Becqure - 1Bq = 1 disintegration/s

Nuclear fission

. Neutron is absorbed

. Nucleus becomes unstable

. Splits into 2 lighter nuclei

. fission neutrons are released

. Chan reaction caused

. Mass of product = less than original

. Energy released

Fission Disadvantages

. Highly radioactive

. extremely dangerous

. Expensive

. Can cause pollution if not stored right

Fission - Political issues

. Creates employment

. shuts down fossil fuel industries = jobs lost

. expensive to commission/ decommission

. Can create weapons

Fission - environmental issues

. No CO2 produced

. Creates radioactive waste

. Conserves fossil fuels

Fission - Social issues

. Dont want it located near people

. Safety concerns

. Longtime necessity

Nuclear Fusion

combining two light nuclei to create a heavy nucleus

Why is energy released?

mass defect - converted to energy - released during reaction

Process

. happens in our sun and stars

. heat of 15000000•c needed

. nuclei moving fast enough to fuse

. energy produced

.reaches earth as electromagnetic radiation

Isotopes that fuse

Hydrogen 2 + Hydrogen 3

Energy released

4 million x the amount from chemical reactions

Fusion - Advantages

. no long lived waste

. more energy than fission

. Big supply of materials

. unlimited supply of energy for earth

Fusion - disadvantages

. very high temp needed

. keeping temp high for long enough

. containment problems

. Sustaining the reaction