(a) Write the formula and describe the structure of a noble gas species which is isostructural with
(b) Assign reasons for the following :
(i) is kinetically inert.
(ii) is an exothermic compound whereas is not.
(iii) HCl is a stronger acid than HF though flourine is more electronegative than chlorine.
(a) (i) : It has 2 bond pairs and 3 lone pairs. Therefore according to VSEPR theory it should have Linear structure. has (7+27+1) i.e. 22 valence electrons. No noble gas has 22 electrons
The isoelectronic species for
(ii) : It has 3 bond pairs and 1 lone pair of electrons. Therefore according to VSEPR theory it has pyramidal structure.
It has 26 valence electrons i.e. (7+36+1=26).
A noble gas having 26 valence electrons is (8+36=26). Thus also has pyramidal structure.
(b) (i) Because is showing steric hindrance due to 6 (six) fluorine atoms which make it unable to react further with any other atom.
(ii) Due to smaller size of F as compared to Cl, the N-F bond is much stronger than N-Cl bond while bond dissociation energy of is much lower than that of . Therefore, energy released during the formation of molecules is more than the energy needed to break and molecules into individual atoms. In other words, formation of is an exothermic reaction.
The energy released during the formation of molecule is less than the energy needed to break and molecule into individual atoms. Thus formation of is an endothermic reaction.
(iii) Because HCl has large size and less bond strength than HF which makes easier liberation of .