Question

Identify metal halide from following having highest ionic character? (M = metal atom)

• A. MF
• B. MBr
• C. MI
• D. MCl

Hint:

Fajan's Rules made simple: Small cation + Large anion = Highly Covalent. Large cation + Small anion = Highly Ionic. Fluorine is the smallest anion, so it almost always forms the most ionic compounds!

Answer 1

The Correct Option is A

Step 1: Keep the metal fixed.
The cation is the same in every option, so only the halide changes.

Step 2: Use Fajan's idea.
A small, tightly held anion gives more ionic character. A big, soft anion gets pulled out of shape and gives more covalent character.

Step 3: Compare the halides.
Size grows as $\text{F}^- < \text{Cl}^- < \text{Br}^- < \text{I}^-$. Fluoride is smallest and hardest to distort, so MF is the most ionic.
\[ \boxed{\text{MF}} \]