<Ul> <Li> C f (\ displaystyle C_ (f)) is the formal charge . </Li> <Li> N v (\ displaystyle N_ (v)) represents the number of valence electrons in a free atom of the element . </Li> <Li> U e (\ displaystyle U_ (e)) represents the number of unshared electrons on the atom . </Li> <Li> B n (\ displaystyle B_ (n)) represents the total number of electrons in bonds the atom has with another . </Li> </Ul> <Li> C f (\ displaystyle C_ (f)) is the formal charge . </Li> <Li> N v (\ displaystyle N_ (v)) represents the number of valence electrons in a free atom of the element . </Li> <Li> U e (\ displaystyle U_ (e)) represents the number of unshared electrons on the atom . </Li>

According to the lewis definition a base is a(n) ___