MCAT - General Chemistry - Unit 2 - Radioactivity

unstable nuclei =

radioactive

Alpha decay

lose He

minus 2 from the atomic number

Minus 4 from the atomic mass

Alpha decay can be blocked by

Skin, clothing - weakest

Beta minus decay

Lose an electron

add 1 to the atomic number

Mass stays same

Beta minus decay is the most

common type of beta decay

beta minus decay can be blocked by

aluminum, plastic, layer of wood

beta plus decay

Gain an electron

minus 1 from the atomic number

mass stays the same

Beta plus decay releases a

positron

Beta plus decay can be blocked by

electron capture - not energetically possible

gamma decay

no change in mass or number

releases a photon of high energy

Gamma decay can be blocked by

Lead, tungsten, steel, or thick concrete

Gamma decay penetrates well because

It releases no mass or energy

Half-life

The time it takes for half the sample to decay

Shorter half-life =

faster decay

Exponential decay formula

N = N_oe^-kt