The oxidation number of fluorine is -1. Since there are five fluorine atoms in \(ClF_5 \), the total oxidation number due to fluorine atoms is \(5 \times (-1) = -5\).
Let the oxidation number of chlorine be \(x\).
The overall oxidation number of \(ClF_5 \) must be zero. Therefore,
$$x + (-5) = 0$$
$$x = +5$$
Therefore, the oxidation number of chlorine in \(ClF_5 \) is +5.
