Question

Which of the following halogen do not form polyhalide?

• A. F
• B. Cl
• C. Br
• D. I

Answer 1

Answer: (A)

F

Fluorine differs from other halogens in many respects.
1: Small size of (F) atom and of F ion.
2: High ionization energy and electronegativity of fluorine than other halogens.
3: Low dissociation energy of $F_2$ molecule.
4: Due to small size, fluorine forms shorter and stronger bonds with elements other
Than O (oxygen), N (nitrogen) and itself.
5: Ionic fluorine has higher lattice energies than the other halides.
6: fluorine always shows oxidation stat of -1 but other halogens can show oxidation State of -1 but other halogens can show more than one oxidation state i.e. -1, +2, +3, +5, +7
7: Fluorine cannot expand their octet beyond 8, but other halogens can expand their Octet.
8: Fluorine combines with noble gases (kr,xe) to give fluoride but other halogens dont.
9: fluorine does not form oxy-acids but other halogens form oxy acids.
And because of this F doesnt form polyhalides.