There are times when you should request copies of your records: 1  Permanent Change of Station. 2  Deploying. 3  Retiring.
0. EXPERT ANSWER. Double coincidence of wants refers to a situation in a barter system where the goods or services offered by a seller are exactly the same as that required by a buyer and vice versa.
Covalent bond: A chemical bond formed when two atoms share one or more pairs of electrons with each other. Double bond: A covalent bond consisting of two pairs of electrons. Electronegativity: A numerical method for indicating the relative tendency of an atom to attract the electrons that make up a covalent bond.