Valency:An atom’s combining capacity is known as its valency. The valency of the element represents the number of bonds that an atom can form as part of a compound.
An oxide is a category of chemical compound that has one or more oxygen atoms as well as another element in its composition.
The Oxygen atom has a total of 8 electrons, and the electronic configuration is 2, 6.
The oxide ion will have 2 electrons more than the atomic configuration to attain a stable electronic configuration, i.e. 2,8.