Why does carbon 14 undergo radioactive decay?

1 Answer
May 29, 2015

Answer:

Carbon-14 is radioactive because it has too many neutrons for the number of protons.

Explanation:

The principal factor that determines whether a nucleus is stable is the neutron to proton (n:p) ratio.

The diagram below plots the number of neutrons versus the number of protons in the first 15 elements.

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The black squares represent stable isotopes. They are called the band of stability for these elements .

For most of these elements, n:p =1.

Carbon-14 has 8 neutrons and 6 protons.

It is unstable because it is above the band of stability.

Its n:p ratio is 8:6 or 1.3:1.

It has too many neutrons for the number of protons, but it would become more stable if it could lose a neutron or gain a proton.

One way to do this is by β decay.

#""_0^1"n" → _1^1"p" + _"-1"^0"e"#

β decay accomplishes both of these. It gets rid of a neutron and forms a proton.

For carbon-14, the reaction is

#""_6^14"C" → _7^14"N" + _"-1"^0"e"#

Note that nitrogen-14 has 7 neutrons and 7 protons. Its n:p ratio is 1:1, and it is stable.