Which can be described as a molecule with residual bonding capacity?

Which of the following compounds is covalent?

The table shown below gives the bond dissociation energies $E_{diss}$ for single covalent bonds of carbon $C$ atoms with elements $A, B, C$ and $D.$ Which element has the smallest atoms?

$Bond$	$E_{diss} (kJ \ mol^{-1})$
$C-A$	$240$
$C-B$	$328$
$C-C$	$276$
$C-D$	$485$

Why does $NH_{3}$ have three covalent bonds but not a triple bond?

Which of the following is an electron-deficient molecule?

In which of the following is the maximum covalent character found between non-metallic elements?