91Ó°ÊÓ

• The distribution of electrons in atomic or molecular orbitals of an atom, molecule, or other physical structure is known as electron configuration.
• An unpaired electron could be a single electron that occupies an atom's orbital instead of as a part of a pair. Each of an atom's atomic orbitals (defined by the three quantum numbers n, l, and m) can hold two electrons (electron pair) with opposite spins.

(a) Based on the periodic table, Cr has the atomic number of $24$, therefore it has $24$electrons. Electronic configuration is:role="math" localid="1663413147905" $1{\mathrm{s}}^{2}2{\mathrm{s}}^{2}2{\mathrm{p}}^{6}3{\mathrm{s}}^{2}3{\mathrm{p}}^{6}4{\mathrm{s}}^{2}3{\mathrm{d}}^5$.

When it gains a charge of $+3$, it loses $3$electrons, and will have only $21$ electrons with electron configuration:$1{\mathrm{s}}^{2}2{\mathrm{s}}^{2}2{\mathrm{p}}^{6}3{\mathrm{s}}^{2}3{\mathrm{p}}^{6}4{\mathrm{s}}^{2}3{\mathrm{d}}^1$ with$1$unpaired electron.

(b) Based on the periodic table, Ti has the atomic number of $22$, therefore it has $22$electrons. Electronic configuration is:$1{\mathrm{s}}^{2}2{\mathrm{s}}^{2}2{\mathrm{p}}^{6}3{\mathrm{s}}^{2}3{\mathrm{p}}^{6}4{\mathrm{s}}^{2}3{\mathrm{d}}^2$.

When it gains a charge of $+4$, it loses $4$electrons, and will have only $18$electrons with electron configuration:$1{\mathrm{s}}^{2}2{\mathrm{s}}^{2}2{\mathrm{p}}^{6}3{\mathrm{s}}^{2}3{\mathrm{p}}^6$with $0$unpaired electrons

(c) Based on the periodic table, Co has the atomic number of $27$, therefore it has $27$electrons. Electronic configuration is:$1{\mathrm{s}}^{2}2{\mathrm{s}}^{2}2{\mathrm{p}}^{6}3{\mathrm{s}}^{2}3{\mathrm{p}}^{6}4{\mathrm{s}}^{2}3{\mathrm{d}}^7$.

When it gains a charge of $+3$, it loses $3$electrons, and will have $24$electrons with electron configuration:$1{\mathrm{s}}^{2}2{\mathrm{s}}^{2}2{\mathrm{p}}^{6}3{\mathrm{s}}^{2}3{\mathrm{p}}^{6}4{\mathrm{s}}^{1}3{\mathrm{d}}^5$ with $6$unpaired electrons.

(d) Based on the periodic table, Ta has the atomic number of $73$, therefore it has $73$electrons. Electronic configuration is:$1{\mathrm{s}}^{2}2{\mathrm{s}}^{2}2{\mathrm{p}}^{6}3{\mathrm{s}}^{2}3{\mathrm{p}}^{6}4{\mathrm{s}}^{2}3{\mathrm{d}}^{10}5{\mathrm{s}}^{2}4{\mathrm{d}}^{10}5{\mathrm{p}}^{6}6{\mathrm{s}}^{2}4{\mathrm{f}}^{14}5{\mathrm{d}}^3$.

When it gains a charge of $+2$, it loses $2$electrons, and will have only $71$electrons with electron configuration:$1{\mathrm{s}}^{2}2{\mathrm{s}}^{2}2{\mathrm{p}}^{6}3{\mathrm{s}}^{2}3{\mathrm{p}}^{6}4{\mathrm{s}}^{2}3{\mathrm{d}}^{10}5{\mathrm{s}}^{2}4{\mathrm{d}}^{10}5{\mathrm{p}}^{6}6{\mathrm{s}}^{2}4{\mathrm{f}}^{14}5{\mathrm{d}}^1$.