Question

What is the daughter nucleus (nuclide) produced when 90Sr undergoes beta decay by emitting an electron?

Answer 1

A beta particle is an electron or a positron, which is emitted from the nucleus. It has no mass, so its loss does not affect the mass of the atom.

During beta-minus (?-) decay, a neutron in the nucleus turns into a proton, an electron and an antineutrino. This is the case with Strontium-90, which undergoes beta-minus (?-) decay to form the daughter nucleus Yttrium-90:

38Sr^90 --> -1e^0 + 39Y^90

The -1e^0 notation reflects that a negative beta particle (or electron) is released.

Note that during beta-minus (?-) decay, the atomic number increases by 1 (in this case, from 38 to 39) while the mass number stays the same (90) as a neutron in the nucleus is transformed into a proton.

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