Atomic Structure

Unstable definition

The ability for a nucleus to decay

Radioactive decay definition

The RANDOM process of radiation being released by a nucleus. A different element in formed

Nuclear radiation definition

The energy and particles released when an unstable nucleus decays

Activity definition

The rate at which a source of unstable nuclei decay

Becquerel definition

The unit of activity

Geiger-Muller tube definition

A device to measure the count rate of a radioactive source

Count rate definition

The number of radioactive decays recorded by a detector per second

Ionising power definition

How well it knocks off electrons and damages cells

Half life definition

The time it takes half of a group of radioactive nuclei to decay

Radioactive contamination definition

Unwanted presence of radioactive atoms on other materials- hazardous- decay of atoms- release radiation- lasts for long period of time, source of radiation transferred

Peer review definition

When the findings of one expert are double checked by another expert to make sure they are correct- essential on effect of radiation on humans- if initial studies get wrong- safety levels based on study cause people to die

Alpha (a) : made of, charge, range in air, penetration and ionising power

• helium nucleus

• +2

• 5cm

• blocked by paper and skin

• high

loses two from proton number and 4 from mass number

Beta (β) : made of, charge, range in air, penetration and ionising power

• fast moving electron

• -1

• 15cm

• blocked by thick aluminium

• medium

loses neutron gains proton, proton number increases by 1 BUT atomic mass doesn’t change

Gamma (γ) : made of, charge, range in air, penetration and ionising power

• electromagnetic wave

• no charge

• very long range

• blocked by thick lead

• low

no change

describe it as a diagram

matched up

Irradiation definition

Lasts short period of time, source emits radiation- reaches object, exposed to radiation- doesn’t become radioactive

Net decline definition

half number of nuclei, and keep doing so after X number of times

• net decline = initial number - number after X half lives/ initial number

Long half life

Doesn’t remain strongly radioactive- initially very radioactive- dies down, less of long-term risk

Short half life

Remains weakly radioactive for long period e.g. americium in smoke alarms (alpha emitter), emitted into air, doesn’t reach far as alpha is weakly penetrating. If smoke reaches, amount of alpha particles drop- alarm sounds

1st model of atom

Dalton- ball, solid sphere

2nd

Plum pudding- sphere positive charge- negative electrons embedded

3rd

Rutherford- nuclear, positive nucleus in centre of atom and electrons in cloud around nucleus

Scattering experiment

• alpha particles fired at sheet of gold foil

• most went straight through- most atom empty space

• some deflected- nucleus must be charged positively- deflecting positive charge of gold

• some deflected straight back- nucleus contained most of mass

3rd and 4th

Bohr- shells around atom

Chadwick- neutron