Question

Consider the species CH₄, `"NH"_4^+` and `"BH"_4^-`. Choose the correct option with respect to these species.

विकल्प

• They are isoelectronic and only two have tetrahedral structures. 

• They are isoelectronic and all have tetrahedral structures. 

• Only two are isoelectronic and all have tetrahedral structures.

• Only two are isoelectronic and only two have tetrahedral structures.

Answer 1

They are isoelectronic and all have tetrahedral structures.

Explanation:

Number of electrons in CH₄ = 6 + 4 = 10

Number of electrons in `"NH"_4^+` = 7 + 4 – 1 = 10

Number of electrons in `"BH"_4^-` = 5 + 4 + 1 = 10

Since, CH₄, `"NH"_4^+` and `"BH"_4^-`, all have equal number of electrons, i.e., 10, so these compounds are isoelectronic.

\[\begin{array}{cc} \ce{H}\\ |\\ \ce{C}\\ /\phantom{..}|\phantom{..}\backslash\\ \ce{H}\phantom{..}\ce{H}\phantom{..}\ce{H}\\ \end{array}\]

\[\begin{array}{cc} \ce{H}\\ |\\ \phantom{..}\ce{N^⊕}\\ /\phantom{..}|\phantom{..}\backslash\\ \ce{H}\phantom{..}\ce{H}\phantom{..}\ce{H}\\ \end{array}\]

\[\begin{array}{cc} \ce{H}\\ |\\ \phantom{..}\ce{B^⊖}\\ /\phantom{..}|\phantom{..}\backslash\\ \ce{H}\phantom{..}\ce{H}\phantom{..}\ce{H}\\ \end{array}\]

They all have tetrahedral structures (sp³ hybridisation).