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.
Protons are particles in the nucleus of an atom that have a positive charge. Electrons are particles that have a negative charge. Therefore, an element in a neutral state will have the same number of protons and electrons. For example, boron (B) has an atomic number of 5, therefore it has 5 protons and 5 electrons. However, if the element includes a negative or positive ion, then the protons and electrons will not be the same. You will have to calculate them. The ion number will appear as a small, superscript after the element.