BIOL 1201 : Exam 1 Review Session
Document Summary
Valence electrons: the electrons in the outermost shell. The shells build out the way the periodic table is built: electronegativity: attraction for electrons (how much does an atom want the electrons?) Ionic: an electron is taken away from another atom (greater than or equal to 1. 7) [non-polar] covalent: bonds where the electrons are shared equally with the two atoms; classic case = two atoms are the same element (less than or equal to 0. 5) (c-h); like tug of war with two equal opponents. H-h (two hydrogens: polar covalent: the electrons are shared unequally; one element wants the electrons more than the other but not enough to take it away (0. 6 to 1. 6) Bonds affect polarity because when electrons are given or taken it affects the charge of the atom (17 protons to 18 electrons [negative]; 11 protons to 10 electrons [positive]) Polar or non-polar based on the bonds that are holding the atoms together.
