Question

Which of the following ions has tetrahedral geometry and $s p^{3}$ -hybridisation for its central atom?

• A. $BH _{4}^{-}$
• B. $NH _{2}^{-}$
• C. $CO _{3}^{2-}$
• D. $H _{3} O ^{+}$

Answer 1

Answer: (A)

(a) Boron-hydride ion $\left( BH _{4}^{-}\right)$ has $s p^{3}$ -hybridisation. Therefore, it is tetrahedral geometry.



(b) In $NH _{2}^{-}$ molecule, the number of sigma bond is 2 and the number of lone pairs is 2 , i.e. $s p^{3}$ -hybridisation. Due to presence of 2 lone pairs, $NH _{2}^{-}$ molecule will be bent shape similar to water.



(c) The carbonate ion, $CO _{3}^{2-}$ has a trigonal planar geometry, i.e. carbon is $s p^{2}$ hybridised.



(d) In $H _{3} O ^{+}$, hybridisation of oxygen is $s p^{3}$ and structure of $H _{3} O ^{+}$ ion will be pyramidal.