Which statement below correctly identifies a rule for assigning oxidation numbers?
a
Hydrogen in most compounds has an oxidation number of -1.
b
Group VIIA (7A) elements have an oxidation number of -1.
c
Group IA (1A) elements have an oxidation number of -1.
d
Oxygen in most compounds has an oxidation number of +2.
e
Group IIA (2A) elements have an oxidation number of -2.
b
Group VIIA (7A) elements (also known as the halogens, which include fluorine, chlorine, bromine, iodine, and astatine) typically have an oxidation number of -1 when they are not combined with an element that is more electronegative (such as oxygen or other halogens).
The other statements have inaccuracies:
a) Hydrogen has an oxidation number of +1 in most compounds (except for metal hydrides where it is -1).
c) Group IA (1A) elements (alkali metals) have an oxidation number of +1.
d) Oxygen typically has an oxidation number of -2 in most compounds (except in peroxides where it is -1, in superoxides where it is -1/2, or when bonded to fluorine).
e) Group IIA (2A) elements (alkaline earth metals) have an oxidation number of +2.