Transcript Radiometric Dating

Radiometric Dating
Half-life
Radioactivity
• Radioactive Isotopes are unstable and
emit/capture elemental particles, causing
them to change over time.
• Parent isotope – the original radioactive
element
• Daughter isotope – the decay product;
what the parent changes into
Half Life
The time it takes for EXACTLY HALF of
the unstable, parent isotope to decay.
This decay occurs at a CONSTANT RATE.
• The half life is NOT affected by:
– Time
– Concentration of parent isotopes
– Heat/pressure
– Breakage/Crushing
Decay
1 half life
50 % parent
2 half lives
100% parent
50% daughter
25% original parent
6.25% parent
12.5% parent
75% daughter
4 half-lives
93.75%
daughter
87.5%
daughter
3 half-lives
Decay Table
Half Lives
elapsed
0
1
2
3
4
% parent
remaining
% daughter
created
Decay
100 %
% of Original Parent
75%
50%
25%
0%
0
1
2
3
HALF LIVES
4
5
Types of Decay
Alpha Decay – an atom emits 2 protons and 2
neutrons
Atomic number and mass decrease
Types of Decay
Beta decay – a neutron breaks into a proton
and an electron…the electron is emitted
atomic # ↑, atomic mass unchanged
Types of Decay
Electron capture –
one electron is
captured by the
nucleus
Atomic number
increases by 1