Download Notes #3

Chemistry
Chapter 4
Notes #3 (Sec 4)
Unstable Nuclei

Nuclear Reactions
– Rxns that involve a change in the nucleus
of an atom (most only involve e- changes)

Radioactivity
– When substances spontaneously emit
radiation

Radiation
– Rays and particles emitted by radioactive
material
Unstable Nuclei
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By emitting radiation atoms of one
element can change into atoms of
another element
This happens because the nuclei is
unstable
Atoms gain stability by losing energy
(ex. Pencil falling over)
Unstable Nuclei

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Unstable nuclei will lose energy by
emitting radiation in a spontaneous
process (so it doesn’t require energy)
called radioactive decay
They undergo decay until they form
stable non-radioactive atoms of a
different element.
Radiation-Alpha

Positively charged alpha particles
– Deflected toward a negative plate
– Alpha particle – 2 p+ and 2 n0
4 He or α
– Symbol
2


Nuclear Equation shows atomic # and
mass # of the particles involved
Ex. Alpha decay- Radium-226 into radon-222
Radiation - Beta

Negatively charged beta particles
– Deflected toward a positive plate
-with a -1 charge
– symbol: 0-1ß

Ex. Carbon-14 into Nitrogen-14
Radiation - Gamma

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
Not deflected by electric or magnetic
fields
High energy radiation with no mass
accompanies alpha and beta radiation
Denoted by the symbol: 00У
Unstable Nuclei

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Atoms containing too many or too few
neutrons are considered unstable
Stability is based on the ratio of
neutrons to protons
The END!