What do an orgasm, a multiplication problem and a photo of a dead body have in common? Each induces a slight, irrepressible expansion of the pupils in our eyes, giving careful observers a subtle but meaningful signal that thoughts and feelings are afoot. For more than a century, scientists have known that our pupils respond to more than changes in light.
Review. 1  Atoms have their electrons arranged in layers called shells. 2  In order to maintain electrical balance the number of electrons is equal to the number of protons in most elements.
Thanks. Obviously atomic number = no of protons = total number of electrons in an atom. Sodium 2,8,1 (1s1 2s2 2p6 3s1) has 13 electrons and is a group 1 element so has 1 valence electron (1 electron in outer shell).