Which of the following atoms would
form a solid metal with the highest melting point?
We have been given five options
labeled from (A) to (E). The question asks us which of the
following atoms would form a solid metal. But as the first electron shell can
only contain a maximum of two electrons, option (B) has a full valence shell of
electrons and it has the electron configuration of a noble gas. It cannot form a solid metal. Thus, we can rule out option (B) as
the answer to this question. We need to figure out which of the
other atoms would form a metal with the highest melting point. The melting point and boiling point
of any metal depend on the size of its cations. The atoms form cations by losing
their valence electrons. These are the cations that would
form from the atoms in (A), (C), (D), and (E) if they lost their valence
Generally speaking, small cations
have high melting points, as the small cations can pack more closely together. This generates strong metallic
bonding forces, and the reverse is true. Generally speaking, large cations
have low melting points. As the question asks for the metal
with the highest melting point, this is most likely to belong to one of the smaller
cations. The cations formed from the atoms
in (A) and (D) are large, whereas the cations formed from the atoms in (C) and (E)
are considerably smaller. We can therefore exclude options
(A) and (D) as possible answers to this question.
The key difference between the
remaining options, (C) and (E), is the number of valence electrons. As option (C) has two valence
electrons and it’s likely to lose both of these electrons, it’s most likely that it
will form a cation with a two plus charge. And as the atom in option (E) has
one valence electron, it’s most likely that it will form a cation with a one plus
charge. So the cation formed in (C) has a
higher charge than that of the cation formed from (E). And as the valence electrons in the
atom form the delocalized electrons in the metal, the metal formed from (C) will
have more delocalized electrons than the metal formed from (E).
Generally speaking, a metal
containing cations with a higher charge and higher concentration of delocalized
electrons will have a higher melting point or boiling point. This is because cations with a
higher charge will have stronger attractions with the delocalized electrons. And the more electrons there are,
the more interactions there will be. As the cation formed from the atom
in (C) has a higher charge than the cation formed from the atom in (E) and the metal
containing the cation in (C) has more delocalized electrons than in (E), we can
conclude that (C) would form a metal with the highest melting point.
So the answer to the question
“Which of the following atoms would form a solid metal with the highest melting
point?” is (C).