Question

Give two examples to show the anomalous behavior of fluorine.

Answer 1

Hint: Fluorine is an element that belongs to the Halogen family. It is placed in Group 17 and Period 2 in the periodic table and is a ‘p’ block element. The anomalous behavior of fluorine is due to its small atomic size and also due to the absence of d orbitals in its outermost shell unlike other halogens.

Complete answer:
As I already mentioned Fluorine is said to have exceptional properties, let us see a few examples regarding it. One of the exceptions is bond energy. The bond dissociation energy should actually decrease down the group as atomic size is increasing but in the case of halogens the order is \[C{l_2} > B{r_2} > {F_2} > {I_2}\].
According to the trend, fluorine should have high bond dissociation energy. The reason for its low bond energy is attributed to its smaller atomic size and also due to repulsion between the three lone pairs on the F atom and the bond pair. The other exception of fluorine is its oxidation state. As halogens are the most electronegative elements, they show a common oxidation state of ‘-1’. Other elements except fluorine can also show different oxidation states like +1, +3, +5 and+7 due to the presence of d-orbitals. As I mentioned fluorine is a p block element and doesn’t have vacant d orbitals to expand its octet, it cannot show higher oxidation states like other halogens. These are two examples of exceptional properties of fluorine.

Note:
Because of its low bond energy, fluorine is said to be a highly reactive element. There are some other exceptions like, all the other halogens can form many oxoacids and have tendency to form polyhalides whereas fluorine can form only one oxoacid and cannot form a polyhalide. Fluorine is also said to have high hydration energy than other elements