I am reading "Book of proof" of Richard Hammard and it says that given the set $E=\{ 1, \{2,3\}, \{2,4\} \}$, we have that $2\not\in E$ . I do not understand why is it so. I understand that the set $E$ is a collection of the elements "$1$", "$\{2,3\}$" and "$\{2,4\}$". But I do not understand why I could not go further and deduce that since $2\in\{2,3\}$ and $\{2,3\}$ is an element of $E$ then $2$ must be an element of $E$.
Sorry if this is a very basic question but I do not even seem to know how to ask for this clarification.