How does electron capture affect the neutron-proton ratio?

1 Answer
Oct 7, 2014

Electron capture increases the neutron-proton ratio.

Electron capture is a process in which a nucleus with too many protons absorbs an electron from an inner orbital.

This changes a proton to a neutron and simultaneously emits an electron neutrino.

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For example.

#""_-1^0"e" + _4^7"Be" → _3^7"Li" + ν_e#

The #""_4^7"Be" # has 4 protons and 3 neutrons.

After electron capture, the new #""_3^7"Li"# has 3 protons and 4 neutrons. The #n:p# ratio is 4:3 = 1.33:1.

The #n:p# ratio has increased from 0.75:1 to 1.33:1. So electron capture has increased the n:p ratio.

A nucleus with too many protons lies below the band of stability.

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It will undergo either electron capture or positron emission to reduce the number of protons (and increase the number of neutrons) to get back to the band of stability.