Among $\mathrm{K}, \mathrm{Ca}, \mathrm{Fe}$ and $\mathrm{Zn}$, the element which can form more than one…
Among $\mathrm{K}, \mathrm{Ca}, \mathrm{Fe}$ and $\mathrm{Zn}$, the element which can form more than one binary compound with chlorine is:
$\mathrm{Fe}$
$\mathrm{Zn}$
$\mathrm{K}$
$\mathrm{Ca}$
Solution
Metal ions having variable oxidation number can form more than one types of binary compound. Fe shows $+2,+3$ oxidation states. Thus, it can form $\mathrm{FeCl}_3, \mathrm{FeCl}_2$.
Related Theory
Binary compounds are chemical compounds comprising of two distinct elements. For example, water, calcium chloride etc.
Caution
$\mathrm{Zn}$, even being a transition metal shows only +2 oxidation state, due to fully filled $3 d$ subshell.