Question

Which oxidation number of iodine is fractional
A)IF3
B)IF5
C)I3-
D)IF7

Answer 1

HOLA MATE UR ANSWER AS FOLLOW....

-Option "C" is the right answer that is I3-

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Answer 2

Here, let's number the iodine atoms. Let the top one be I1I1, the middle one be I2I2 & the lower one be I3I3. From the structure, it is clear that I1I1 & I3I3have shared only one electron. So their oxidation states would be either +1 or -1, we'll see that later. Now consider I2I2, it has gained one electron & shared two electrons. So it's oxidation state would be +3 or -3. I2I2 is sp³d hybridized, so it has 2 paired & 3 unpaired electrons. Out of 3 unpaired electrons, 2 are paired by sharing with I1I1 & I3I3, the remaining is paired by gained electron.

You have to know that electronegativity of s,p,d&f orbitals go on decreasing as s>p>d>f. Now, each orbital of I2I2 os sp³d hybridized i.e. each orbital has 20% s-character, 60% p-character & 10% d-character. So each sp³d orbital of I2I2 is more electronegative than single p-orbital I1I1 & I3I3. So I2I2 is more electronegative than I1I1 & I3I3. So oxidation state of I2I2 will have negative sign & that of I1I1 & I3I3 will have positive sign. So the total oxidation state of I3I3 = (+1)+(-3)+(+1) = -1, which matches with the charge on the ion.

So, The terminal iodide atoms have +1 oxidation state whereas the central iodide atom will have -3 oxidation state.