The mass number plays an important role for elements and their isotopes. Mass number comes from the addition of protons and neutrons (their weight). Isotopes are the elements, but with a different number of neutrons. So in turn, by subtracting the number of protons (atomic number) from the mass, you can find the number of neutrons.
is the Lewis base in the following reaction:
→ 
<h3>What is lewis base? </h3>
Lewis base is a species that donates an electron pair.
In the above-given chemical equation, the
is the lewis base which is donating an electron pair to the central atom of
to form
.
Hence,
is the Lewis base in the following reaction:
→ 
Learn more about the lewis base here:
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