Use the periodic table to determine the electron configuration for Ca and Pm in noble-gas notation Ca: [Ar]4s2 [Ar]4s1 [Ar]3s2 [
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Answer:
Missing particles: (a positron) and an electron neutrino
.
The nuclear equation would be:
.
Explanation:
The mass number of a particle is the number on the top-right corner of its symbol.
The atomic number of a particle is the number on the lower-right corner of its symbol.
The nuclear reaction here resembles a beta-plus decay. The mass numbers of the two nuclei are equal. However, the atomic number of the product nucleus is lower than that of the reactant nucleus by .
A beta decay may either be a beta-plus decay or a beta-minus decay. In a beta-plus decay, a positively-charged positron and an electron neutrino
would be released. On the other hand, in a beta-minus decay, a negatively-charged electron
and an electron antineutrino
would be released.
Electric charge needs to be conserved in nuclear reactions, including this one.
The atomic number of the nucleus on the left-hand side is
, meaning that the nucleus has a charge of
. On the other hand, the atomic number of the
nucleus on the right-hand side shows that this nucleus carries a charge of only
.
By the conservation of electric charge, the particles on the right-hand side must carry a positive charge of . That rules out the possibility of the combination of one negatively-charged electron
(with a charge of
) and an electron antineutrino
(with no electric charge at all.)
Hence, the only possibility is that the missing particle is a positron (and an electron neutrino , which carries no electric charge.)