<span> By definition, </span>oxidation number<span> is the charge left on the given atom when all the bonding pairs (of electrons) are broken, so the oxidation number of Br will be +1</span>
Reactivity trends of halogen:
1) Melting point and boiling points increased down the
group
2) Colour becomes darker.
E.g. Fluorine (pale yellow)
Chlorine (yellowish-green)
Bromine (reddish-brown)
Iodine (purplish-black)
Astatine (black)
3) The reactivity decreases down the group.
Reactivity:
F > Cl > Br > I > At
The scientist observes at what rate is the concentration increasing or decreasing.
