Asecond important result is that electrons will fill the lowest energy states available. this would seem to indicate that every electron in an atom should be in the n=1 state. this is not the case, because of pauli's exclusion principle. the exclusion principle says that no two electrons can occupy the same state. a state is completely characterized by the four numbers n, l, ml, and ms, where ms is the spin of the electron. an important question is, how many states are possible for a given set of quantum numbers? for instance, n=1 means that l=0 with ml=0 are the only possible values for those variables. thus, there are two possible states: (1, 0, 0, 1/2) and (1, 0, 0, −1/2). how many states are possible for n=2? express your answer as an integer.

Consider the following geometry problems in 3-space enter t or f depending on whether the statement is true or false. (you must enter t or f -- true and false will not work.) f equation editorequation editor 1. a plane and a line either intersect or are parallel t equation editorequation editor 2. two planes parallel to a third plane are parallel f equation editorequation editor 3. two lines either intersect or are parallel f equation editorequation editor 4. two planes orthogonal to a third plane are parallel f equation editorequation editor 5. two planes orthogonal to a line are parallel f equation editorequation editor 6. two planes either intersect or are parallel f equation editorequation editor 7. two lines orthogonal to a third line are parallel t equation editorequation editor 8. two lines parallel to a third line are parallel t equation editorequation editor 9. two planes parallel to a line are parallel f equation editorequation editor 10. two lines parallel to a plane are parallel f equation editorequation editor 11. two lines orthogonal to a plane are parallel