Question

Which of the following statement(s) is/are correct?

• A. The hybrid state of $Be$ in $BeC{l}_2$ in solid state is $s{p}^3$
• B. The hybrid state of $Be$ in $BeC{l}_2$ in vapour state is $sp$
• C. $Be{H}_2$ is a covalent and polymeric compound
• D. The ionic character of group II halides follows the order:
  $Be{X}_2>Mg{X}_2>Ca{X}_2>SrX2$

Answer 1

Answer: (A), (B), (C)

The correct options are
A The hybrid state of $Be$ in $BeC{l}_2$ in solid state is $s{p}^3$
B The hybrid state of $Be$ in $BeC{l}_2$ in vapour state is $sp$
C $Be{H}_2$ is a covalent and polymeric compound

a) In solid state, $BeC{l}_2$ exists as a polymer and each $Be$ is bonded to four $Cl$ atoms . Thus $Be$ is $s{p}^3$ hybridised here.
b) In vapour state, $BeC{l}_2$ exists as a linear molecule (monomer) and hence, $Be$ is $sp$ hybridised.
c) $Be{H}_2$ is a covalent and polymeric compound because of electron defficiency.
d) The ionic character of group II halides follows the reverse order that is given in the option, since according to Fajan's rule polarising ability decreases down the group so covalent character decreases down the group.