Question

What is the electron configuration of `"H"^-`?

Answer 1

Well, what's the configuration of `"H"` plus one electron? `"H"` notoriously has only one electron... and it is in the `1s` orbital, the first orbital of `n = 1` and `l = 0`. Therefore, its electron configuration can only be `1s^1`.

...and `"H"^(-)` has `1 + 1 = 2` electrons by conservation of charge... so `1s^?` is the electron configuration?