Question

Which statement is correct about halogens?
A. They are all diatomic and form univalent ions.
B. They are all capable of exhibiting several oxidation states.
C. They are all diatomic and form divalent ions.
D. They can mutually displace each other from the solution of their compounds with metals.

Answer 1

Hint: Free halogens are not found in our nature because of their high reactivity. Among all halogens, fluorine is the most abundant element found in nature in combined form. To approach the above question, we will have to study about different physical and chemical properties of halogens.

Complete step by step solution:
Halogen compounds belong to group-17 in the periodic table. They are fluorine(F),Chlorine(Cl), Bromine(Br), Iodine(I) and Astatine(At) respectively. Some important physical properties are written below:
Physical properties:
a. They are all non-metals.
b. Only fluorine and chlorine are gas but bromine, iodine, and astatine are solid.
d. All halogen elements are homonuclear diatomic. For example, $F_2,C{l}_2,B{r}_2,I_2$ etc.
e. Except for fluorine, all halogens show several oxidation states $\text{-1,+1,+3,+5and+7}$.
f. Halogen compounds have seven valence electrons, hence they gain one negative by reacting with another molecule to complete their valence shell.
g.They are good reducing agents and highly reactive elements.

So, from the given option it is found that option (A) is correct because all halogens are diatomic and form univalent ions such as $F^{-},C{l}^{-},B{r}^{-}$ , etc. (B) is not right as fluorine is capable of exhibiting only one oxidation state $-1$. (c) is also the wrong option. Halogens participate in displacement reactions with metal halogen compounds, but not all the time they can displace each other. When fluorine reacts with sodium chloride (NaCl), fluoride displaces chloride and forms sodium fluoride (NaF).
$F_2(aq.)+2NaCl(aq.)\to 2NaF(aq.)+C{l}_2(aq.)$

A more reactive halogen always displaces a less reactive halide from its compounds in that particular solution. If bromine is added to the solution of potassium fluoride(KF), here bromide can not displace fluoride as $B{r}^{-}$ is less reactive $F^{-}$. Hence, option (D) is wrong.
Thus, option (A) is correct.

Note: Halogen molecules react directly to form interhalogen compounds such as $Br{F}_3,Cl{F}_3$etc. They are covalent in nature. The bonds formed between interhalogen compounds are more reactive than diatomic halogen bonds. These compounds are used as non-aqueous solvents and catalysts in many reactions.