P4

Isotope

Atoms with the same atomic number but a different mass number

Radioactive Decay

Unstable isotopes decay into other elements and spit out radiation as they try to become more stable

Radioactive Decay Spits Out

Apha
Beta
Gamma
Neutrons

Ionising Radiation

Knocks electrons off atoms
Creating positive ions

Ionising Power

How easily they can do this

Alpha Particles

Helium Nuclei

Alpha Radiation

When an alpha particle is emitted from a nucleus
Two protons and two neutrons

Penetration of Alpha

Not very as they can only travel a few cm in the air and are absorbed by a piece of paper

Ionising of Alpha

Strongly Ionising

Beta Particles

High speed electrons emitted from a nucleus
No mass
Charge of -1

Penetration of Beta

Moderately Far

Beta Ionising

Moderately Ionising

Beta Range in Air

Few metres
Absorbed by a sheet of aluminium

Gamma Rays

Electromagnetic waves with a short wavelength released by the nucleus

Gamma Penetration

Far into materials
Absorbed by thick lead or metres of concrete

Gamma Ionising

Weakly ionising tends to pass through materials rather than collide with atoms

Nuclear Equations

Show radioactive decay using elemental symbols
Atom Before Decay --> Atom After Decay

Golden Rule of Nuclear Equations

Total Mass and Atomic Numbers must be equal on both sides

Alpha Decay

Made up of two protons and two neutrons
When an atom emits an alpha particle, its atomic number reduces by two and its mass number by four
Charge decreases

Beta Decay

Neutron is turned into a proton and a fast-moving electron is released
Increase in positive charge and therefore the atomic number
0-1e

Gamma Decay

Ways of getting rid of excess energy
No change in mass or atomic number

Half Life

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

Why can you not predict when a nuclei will emit radiation

Because radioactive decay is a totally random process

Why do we use Half Life?

Makes predictions about radioactive sources

Activity

The rate at which a source decays
Bq (1Bq is 1 decay per second)