Bases are compounds which have the tendency to liberate hydroxide ions, or donate electrons or accept protons.
These are three different definitions of base which are based on the availability of hydroxide ions, availability of electrons or unavailability or capability to accept protons. Complete step-by-step answer:
In order to answer this question at first we need to define the terms acid and bases and how can we identify both.
A substance which has the capability to donate electrons to any other species, are termed as bases. And the substances which have the tendency to accept electrons are termed as acids. Now, acid and bases can also be defined in terms of hydrogen or proton accepting and donating or liberating capabilities. If a substance liberates protons as soon as it comes in contact with an aqueous solution, then it would be termed as an acid. And if a substance can accept protons, is termed as a base.
We need to know there is something called conjugate base and conjugate acids. The conjugate base of an acid is the species which arises when an acid loses a proton and becomes negatively charged ion. So, the dichromate ion is a conjugate base of hydrogen dichromate. The structure of this species can be represented as, Note:
So, as we can see there are seven oxygen atoms attached to two chromium atoms and two of the oxygen atoms have negative charge. Since, this ion has availability of negative charge, it can easily donate the electrons and hence it is a type of base.