Draw the structure of H 3 PO 3 .

H 3 PO 3 is called orthophosphorous acid or phosphorous acid. It is one of the phosphorus oxygenic acids. Phosphorous acid ( H 3 PO 3 ) forms salts known as phosphites which are sometimes used as reduction agents. The structure of H 3 PO 3 is

Draw the structure of HClO 4 .

Perchloric acid ( HClO 4 ) is an oxoacid of chlorine, which contains one hydroxyl group attached to the central chlorine atom, and three chlorine to oxygen double bonds. Therefore, the structure of HClO 4 can be written as given below:

Explain why ICl is more reactive than I 2 .

ICl is a polar compound because of the difference in electronegativity. While I 2 is halogen molecule which is non polar in nature. The bond length of ICl is greater than I 2 so the bond of ICl breaks easily then I 2 , so ICl is more reactive than I 2 .

Explain why helium is used for filling weather balloons.

Helium is used for filling weather balloons because of two reasons: 1. It is lighter than air as its density is about one-eighth to that of air, therefore can go upward in air for weather forecasting. 2. It is inert and non-inflammable, therefore will have no risk of explosion unlike hydrogen.

Explain why nitrogen does not form pentahalides.

Valence shell electronic configuration of nitrogen is 2 s 2 2 p 3 . Therefore, it can accommodate maximum of three electrons in its valence p -orbital. As nitrogen does not have d -orbital, so it cannot increase its Co- ordination number. So it cannot form pentahalides.