Question

The ionic character of $M - X$ bond decreases in the order of:
A. $M - F > M - Cl > M - Br > M - I$
B. $M - I > M - Br > M - Cl > M - F$
C. $M - Cl > M - Br > M - F > M - I$
D. $M - F > M - I > M - Br > M - Cl$

Answer 1

The ionic character of a chemical compound completely depends on the electronegativity difference between the constituent atoms. Thus the halogen with a higher value of electronegativity will have a higher ionic character in it along with some traces of covalent character (may or may not).

Complete step by step answer:

Every chemical bond consists of both ionic as well as covalent character. The ionic character of a chemical bond depends upon the electronegativity difference between the adjacent atoms forming the chemical bond. The greater the electronegativity difference, the greater will be the polarity between the atoms and thus, greater the ionic character of the compound. In the case of metal halides, the electronegativity value decreases down a group. Thus, the halogen atom placed at the top of the halogen group has a greater tendency of ionic character than the halogens placed below it. The order of the electronegativity in the halogens is as follows:
$- F > - Cl > - Br > - I$
This order also provides a crystal clear knowledge of the order of the ionic character of various metal halide compounds. Therefore, the decreasing order of ionic character is as follows:
$M - F > M - Cl > M - Br > M - I$
Thus, the correct option is A. $M - F > M - Cl > M - Br > M - I$ .

Note:
Every chemical bond shows two types of character. One is an ionic character and the other is the covalent character. If a bond has an ionic character of $70\%$ , this means that it should have a covalent character of $30\%$ . This also signifies that the bond is a result of both electronic polarity as well as mutual sharing of electrons between the two adjacent atoms.