Question

How do I identify the number of valence electrons present for something like magnesium? so like the electron configuration is 1s^2 2s^2 2p^6 3s^2, but what do I do next?

Answer 1

the valence level of an atom's electrons is always the highest occupied level (the largest value of n). Magnesium has 12 electrons, but only 2 of them are valence electrons.