Question

Which of the following substances has the least ionic character?

• A. ${FeCl}_2$
• B. ${ZnCl}_2$
• C. ${CaCl}_2$
• D. ${MgCl}_2$

Answer 1

The correct option is B

${\mathrm{ZnCl}}_2$

Explanation for correct option

(B) Ionic character:

• The percentage difference in electronegativity between two covalently bound atoms is referred to as ionic character.
• The ability to lose electrons, i.e. ionic character increases as the size of the alkaline earth metal group increases. Hence, ${\mathrm{CaCl}}_2$ has a higher ionic character than ${\mathrm{MgCl}}_2$.
• The s-block compounds are more ionic in nature when compared to transition elements. The exceptions include beryllium and lithium. Hence, ${\mathrm{FeCl}}_2$ and ${\mathrm{ZnCl}}_2$ have less ionic character than ${\mathrm{MgCl}}_2$ and ${\mathrm{CaCl}}_2$.
• In ${\mathrm{ZnCl}}_2$, ${\mathrm{Zn}}^{2+}$ is less electropositive when compared to ${\mathrm{Fe}}^{2+}$ (Electropositive character decreases when moving left to right in a period). Hence, ${\mathrm{ZnCl}}_2$ is the most covalent, or least ionic.

Explanation for incorrect options

${\mathrm{ZnCl}}_2$ has the least ionic character compared to ${\mathrm{FeCl}}_2$, ${\mathrm{CaCl}}_2$ and ${\mathrm{MgCl}}_2$. Therefore, all the other options (A), (C), and (D) are incorrect.

Therefore, the correct option is (B). ${\mathbf{ZnCl}}_{\mathbf{2}}$ has the least ionic character.