# What is the oxidation number of a Group VIIA element in a compound?

Jul 27, 2014

The oxidation number of a Group 7 element depends on the compound it is in.

#### Explanation:

The most common oxidation number for Group 7 elements is -1, as in $\text{HF}$, ${\text{CaCl}}_{2}$, $\text{NaBr}$, and $\text{KI}$.

$\text{F}$ is the most electronegative element in the Periodic Table. It isn't going to give up its electrons.

Its oxidation number in compounds is always -1.

But the other Group 7 elements can have various oxidation states.

For example, $\text{Cl}$ forms compounds with all the oxidation states except +2:

• +1 — in $\text{NaClO}$
• +3 — in ${\text{NaClO}}_{2}$
• +4 — in ${\text{ClO}}_{2}$
• +5 — in ${\text{KClO}}_{3}$
• +6 — in ${\text{Cl"_2"O}}_{6}$
• +7 — in ${\text{KClO}}_{4}$

$\text{Br}$ and $\text{I}$ form compounds with all the above oxidation states except +6 (some of these compounds are unstable).