Download Half-Life

CHAPTER 25 – NUCLEAR CHEMISTRY
Radioactivity – process by which Uranium gives off rays
Radioisotopes – radioactive isotopes; because they are unstable
**Why do radioisotopes undergo radioactive decay???
Types of radioactive decay:
1.) Alpha
2.) Beta
3.) Gamma
Nuclear Stability Plot: Ratio of Neutrons to Protons
**Stable Nuclei do not decay or change over time!!!
Half-Life – Time required for one-half of the atoms of a radioisotope to
emit radiation and to decay to products
**Can anyone think of a use for a radioisotope with a short half-life?
Long half-life?
Example: Nitrogen -13 emits beta radiation and decays to carbon-13
with a t1\2= 10 minutes. Assume a starting mass of 2.00g of Nitrogen.
a.) How long is four half-lives?
One half-life is equal to 10 minutes. Four half-lives is 4 x 10 min =
40 minutes
b.) How many grams of Nitrogen-13 will still exist after three halflives?
Number of half-lives
0
1
2
3
Mass (g)
2.00
1.00
0.50
0.25
Time (min)
0
10
20
30
**Math challenge: Is there an equation you could use to find the same
answer above??
Initial Mass (1\2)x where x = number of half-lives
Transmutation Reactions – Conversion of an atom of one element to an
atom of another element.
Transuranium Elements- All elements above atomic number 92 all
undergo transmutation and do not occur naturally.
Nuclear Fission versus Fusion
Fission – When the nuclei of certain isotopes are bombarded with
neutrons the nucleus splits. Ex- Nuclear Reactors; Atomic Bombs
Fusion – When two nuclei combine to produce a nucleus of heavier mass;
releases more energy than fission. Ex.- Solar Fusion