Question

Among CaH₂ , BeH₂ , BaH₂ , the order of ionic character is

• A. BeH₂ < CaH₂ < BaH₂
• B. BeH₂ < BaH₂ < CaH₂
• C. CaH₂ < BeH₂ < BaH₂
• D. BaH₂ < BeH₂ < CaH₂

Answer 1

The Correct Option is A

The question asks for the order of ionic character among the hydrides CaH₂, BeH₂, and BaH₂.

Concept: The ionic character of a compound typically depends on the difference in electronegativity between the bonded atoms, and in this case, between the metal and hydrogen. A larger metal size and lower electronegativity will typically result in a more ionic character.

Step-by-Step Explanation:

1. The metal hydrides in question are of the alkaline earth metals: Be, Ca, and Ba.
2. As we move down the group in the periodic table, the size of the metal atoms increases and their electronegativity decreases.
3. BeH₂ is more covalent due to the small size of beryllium and its relatively higher electronegativity compared to calcium and barium.
4. CaH₂ and BaH₂ are less covalent and thus have more ionic character as compared to BeH₂.
5. Between CaH₂ and BaH₂, BaH₂ is more ionic than CaH₂ due to barium's larger size and lower electronegativity.

Conclusion: The order of ionic character among these hydrides is BeH₂ < CaH₂ < BaH₂.