Among K, Ca, Fe and Zn, the element which can form more than one binary compound with chlorine is :-
A
Zn
B
K
C
Ca
D
Fe
The answer is D.
Solution
An element forms more than one binary chloride only if it shows more than one stable oxidation state. K (alkali metal) shows only +1: KCl. Ca (alkaline earth metal) shows only +2: $CaCl_2$. Zn has a completely filled $3d^{10}$ configuration and shows only +2: $ZnCl_2$. Fe ($[Ar]\,3d^6\,4s^2$) is a transition element with variable oxidation states +2 and +3. It forms $FeCl_2$ (ferrous chloride) and $FeCl_3$ (ferric chloride). So the element is Fe.
ConceptVariable valency of iron
The d- and f-Block Elements in past papers
76 questions from this chapter have appeared across 27 exam years.
