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Nuclear Chemistry
Radioactivity
• The result of an unstable nucleus
• Three main types– Alpha– Beta– Gamma
Alpha
A helium atomCan result when the nucleus of a large atom
breaks apart.
23892U 234
90Th + 42He
Note that all mass is conserved.238 = 234 + 4
Beta
A high speed electron
A neutron breaks into a proton, changing the number of protons in the nucleus and resulting in a atom of a different element, and an electron that is expelled from the nucleus.
21884Po 218
85At + 0-1e
Mass of atom stays the same.
Gamma Radiation
Gamma ray – photon of light
Emitted when an atom that has released a beta particle “settles” down.
Table of types of Radiation
Half Life
Radioactive decay occurs one atom at a time
Half life is the time requires for half of the atoms that were in the starting sample to decay.
Half life is a constant rate14C – half life around 5700 yrs
Example
Start: 100 g 14C
After 5730 yrs, have 100g/2 = 50g 14C
After another 5730 yrs,
have 50g/2 = 25g 14C
After the next 5730 yrs,
have 25g/2 = 12.5g 14C
14C
Nuclear Fission
Fission – the breaking apart of an atom into smaller parts
Method – neutron “hits” a nucleus of an atom. Energy of collision is transferred to the nucleus. If sufficient, the nucleus breaks into smaller pieces creating two new atoms of other elements.
Mass is conserved.
Example
Manhattan Project
New Mexico - Los Alamos, White Sands
First nuclear bombs
Little Boy – used “critical” mass
Fat Man – conventional explosives compress atoms which then “explode”
Fusion
The Power of the Stars
Small nuclei are fused together to form larger nuclei.
Uses
Nuclear energy- Fission produces MORE radioactive
material than is consumed- Fusion produces massive amounts of
energy and smaller amounts of radioactivity. Not yet available to use on Earth.
- Medicine- Dating/determining ages of things