In NO₃^- ion, the number of bond pairs and lone pairs of electrons on nitrogen atom are

Hydrogen bonds are formed in many compounds e.g., H₂O, HF, NH₃ . The boiling point of such compounds depends to a large extent on the strength of hydrogen bond and the number of hydrogen bonds. The correct decreasing order of the boiling points of above compounds is :

In PO₄^3- ion the formal charge on the oxygen atom of P–O bond is

Which of the following species has tetrahedral geometry?

Number of π bonds and σ bonds in the following structure is–