4. An atom has two electrons with principal quantum number (n) = 1, eight
electrons with principal quantum number (n) = 2 and seven electrons with
principal quantum number (n) = 3. From these data, supply the following values
(if insufficient information is given, say so) in the following order: mass number;
atomic number, electron configuration. Separate your answers with a semi-
colon. (Enter electron configuration as 1s2 2s2 etc.) *