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NEET CHEMISTRYEasy

The correct order of ionic character among CaH2_2, BeH2_2 and BaH2_2 is:

A

BeH2_2 < CaH2_2 < BaH2_2

B

CaH2_2 < BeH2_2 < BaH2_2

C

BeH2_2 < BaH2_2 < CaH2_2

D

BaH2_2 < BeH2_2 < CaH2_2

Step-by-Step Solution

  1. Periodic Trend: The ionic character of hydrides depends on the electropositive nature of the metal. As we move down Group 2 (Alkaline Earth Metals) from Be to Ba, the atomic size increases and the ionization enthalpy decreases .
  2. Electropositivity: Consequently, the electropositive character increases down the group (Be < Ca < Ba).
  3. Fajan's Rule/Bonding: The compounds of s-block elements are predominantly ionic, with the notable exception of Lithium and Beryllium compounds which are largely covalent due to their small size and high ionization enthalpy . Therefore, BeH2_2 is covalent, while CaH2_2 and BaH2_2 are ionic.
  4. Comparison: Since electropositivity increases from Ca to Ba, the ionic character of the bond M-H increases. Thus, BaH2_2 is more ionic than CaH2_2.
  5. Conclusion: The correct order of increasing ionic character is BeH2_2 < CaH2_2 < BaH2_2.
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