Write a note on metal halides. Explain the reactivity of halogens with metals. Write a short note on interhalogen compounds.

(N/A) Halogens react with metals to form metal halides. For example,bromine reacts with magnesium to give magnesium bromide.
$Mg_{(s)} + Br_{2(l)} \rightarrow MgBr_{2(s)}$
The order of reactivity of halogens with metals is: $F_{2} > Cl_{2} > Br_{2} > I_{2}$.
The ionic character of the metal halides decreases in the order: $MF > MCl > MBr > MI$,where $M$ is a monovalent metal.
For example: $NaF > NaCl > NaBr > NaI$ (ionic character decreases).
If a metal exhibits more than one oxidation state,the halides in the higher oxidation state are more covalent than those in the lower oxidation state.
For example: $SnCl_{4}, PbCl_{4}, SbCl_{5}$,and $UF_{6}$ are more covalent than $SnCl_{2}, PbCl_{2}, SbCl_{3}$,and $UF_{4}$ respectively.
Halogens combine among themselves to form a number of compounds with the general formula $XX'_{n}$ (where $n = 1, 3, 5, 7$),known as interhalogen compounds.
$X'$: Smaller size halogen atom.
$X$: Larger size halogen atom.

$X$	$X'$
$I, Br, Cl$	$F, Cl, Br; F, Cl; F$

Interhalogen compounds are formed due to the difference in electronegativities of the halogens. As the ratio between the radii of $X$ and $X'$ increases,the number of atoms per molecule also increases. Thus,iodine$(VII)$ fluoride $(IF_{7})$ has the maximum number of atoms ($8$ atoms) per molecule.