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Nuclear Chemistry
Intro
Chapter 21
Enriched Chemistry
“The Nucleus”
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Early in the periodic table protons ~ neutrons, but this chapter
is about those later elements where this isn’t true… the
number of neutrons greatly exceeds the number of protons
Atoms are mostly empty space
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Weights of subatomic particles
Atoms are so small they have their own unit of
mass – the u
U = unified mass unit, or 1.66 x 10-27 kg
Proton
Mass = 1 u
Charge = +1
Neutron
Mass = 1 u
Charge = 0
Electron
Mass = 1/1836 u
Charge = -1
Neutrons – Why are they important?
Think back to chemistry – what do like charges
do?
Ex. The nucleus is full of positively charged protons
– why don’t they fly apart?
Neutrons get between protons and hold them
apart enough so they don’t repel, but close
enough so other forces hold them together.
This is a lot like the perfect distance for a satellite to
orbit a planet – not drifting away or falling closer
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The Problem
Neutrons stabilize the nucleus, but as an atom
increases in size it needs more and more
neutrons to be stable
If the number and position of neutrons isn’t
perfect, the atom becomes unstable and starts to
release its excess energy
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Chemistry Review…
How do we describe elements?
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Isotope
Def: Atoms with the
same number of
protons as their
element name, but
differing numbers of
neutrons
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Elements higher than 83
These elements have too many protons to be
stable, but they want to be stable.
They get stable by decaying until they are stable
– releasing their extra energy slowly in the form
of ionizing radiation (ultraviolet rays, xx-rays,
gamma rays)
How long will they
decay?
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It depends
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How is this useful?
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Carbon Dating
Def: A technique that estimates the age of
decreased organisms based on the amount of
radioactive carbon-14 remaining in their tissues
Dating Rocks & Fossils
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See Radioactive Decay
pHet simulation
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Uses of Radiation
WWI
the advent of the x-ray
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Examining internal structures
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Nuclear Bombs
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Nuclear Power
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Seeing in metal stuff
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Killing bacteria in food
to prevent spoilage
Irradiation
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Canadians… (unrelated)
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Sterilizing hospital meals
for patients with reduced
immune function
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Smoke Detectors
If smoke blocks the path of radiation
between two points, it goes off
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