Nuclear & Particle Physics - Radioactive

When 74Be transforms into73Li, it does so by

A. emitting an alpha particle only
B. emitting an electron only
C. emitting a neutron only
D. emitting a positron only
E. electron capture by the nucleus with the emission of a neutrino

(GR0177 #68)
Solution:

The stable element Beryllium usually contains 4 protons and 5 neutrons in its nucleus.

However, there exists a lighter isotope of Beryllium, 47Be which contains 4 protons and only 3 neutrons, which give a total mass of 7 amu.

This lighter isotope decays into Lithium-7 through electron capture.

A proton from Beryllium-7 captures a single electron and becomes a neutron.

This reaction produces a new isotope (Lithium-7) that has the same atomic mass unit as Beryllium-7 but one less proton which stabilizes the element.

Answer: E

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