A bond rating is an assessment of the creditworthiness of a bond issuer, which is used to determine the likelihood of the issuer being able to meet its financial obligations. Valence, with seven letters, is the measure of the power of an atom to combine with other atoms. AAA, with three letters, is the highest possible bond rating, indicating that the issuer has a very strong capacity to meet its financial obligations. CCC, also with three letters, is the lowest possible bond rating, indicating that the issuer has a very weak capacity to meet its financial obligations.