The correct order of the increasing ionic character is:

Question

Accepted Answer

The ionic character of a bond is related to the electronegativity difference between the bonded atoms. For a series of compounds with a common anion (Cl in this case) and varying cations from the same group, the ionic character increases down the group.

Concept: Ionic character increases with increasing size of the cation and decreasing charge density of the cation, leading to less polarization of the anion. Down a group, the size of the metal cation increases, and its electronegativity decreases. This results in a greater electronegativity difference between the metal and chlorine, leading to a more ionic bond.

Why (A) is correct: Beryllium (Be), Magnesium (Mg), Calcium (Ca), and Barium (Ba) are all elements of Group 2 (alkaline earth metals). Down the group, the atomic size increases, and the electronegativity decreases. Therefore, the electronegativity difference between the metal and chlorine increases from Be to Ba. This leads to an increase in ionic character in the order: $B e C l_{2} < M g C l_{2} < C a C l_{2} < B a C l_{2}$ .

Option Analysis:

A) $B e C l_{2} < M g C l_{2} < C a C l_{2} < B a C l_{2}$ : This order correctly reflects the increasing ionic character down Group 2.
B) $B e C l_{2} < M g C l_{2} < B a C l_{2} < C a C l_{2}$ : This order is incorrect because $C a C l_{2}$ has less ionic character than $B a C l_{2}$ .
C) $B e C l_{2} < B a C l_{2} < M g C l_{2} < C a C l_{2}$ : This order is incorrect as it mixes up the positions of $B a C l_{2}$ , $M g C l_{2}$ , and $C a C l_{2}$ .
D) $B a C l_{2} < M g C l_{2} < C a C l_{2} < B e C l_{2}$ : This order is incorrect as it represents the decreasing ionic character.

Correct Answer: (A)

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