Indefinite pronouns and agreement

The pronouns each, everyone, every one, everybody, anyone, anybody, someone, and somebody are singular and require singular verbs.

(1) [Each of the contestants] sings well.

(2) [Every one of the experiments] is complete.

(3) It seems as if [everybody] is mistaken.

Everyone is one word when everybody could be used instead. The expression every one consists of two words when the meaning is each one. Neither everyone nor everybody can be followed by an of phrase (so we have to say every one of the experiments, instead of *everyone of the experiments).