Q.(a) ICl7 does not exist while IF7 exist. Why? (2 marks)
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Start your 14-day free trial to unlock the full solution →(a) Steric size mismatch explains why IF7 exists but ICl7 doesn't. (b) Bartlett's analogy between and Xe ionisation energies led him to make the first noble-gas compound, .
(a) does not exist while exists: Iodine is a fairly large atom, and to form a heptahalide, seven halogen atoms must be packed around the central iodine atom. Fluorine atoms are very small in size, so seven of them can be accommodated around the iodine atom without excessive crowding, allowing to exist (pentagonal bipyramidal geometry). Chlorine atoms are considerably bigger than fluorine atoms; seven such bulky chlorine atoms cannot be sterically accommodated around the central iodine atom without severe steric strain, so does not exist (the highest chloro-interhalogen of iodine is only ).
(b) Neil Bartlett's experiments on the reactivity of xenon: Bartlett first prepared the ionic compound dioxygenyl hexafluoroplatinate(V), , by reacting oxygen gas directly with platinum hexafluoride (), a very strong oxidising/fluorinating agent. He noted that the first ionisation enthalpy of molecular oxygen () is almost identical to the first ionisation enthalpy of the xenon atom (). Reasoning that if could oxidise , it should similarly be able to oxidise Xe, he reacted xenon gas directly with vapour at room temperature and obtained an orange-yellow solid, (xenon hexafluoroplatinate). This was the first genuine chemical compound of a noble gas ever prepared, and it overturned the long-held belief that noble gases were completely chemically inert.
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