BIO 201 Lecture Notes - Lecture 2: Ionic Bonding, Octet Rule, Electron Shell

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O(cid:272)tet rule: prefere(cid:374)(cid:272)e for 8 ele(cid:272)tro(cid:374)s i(cid:374) the ato(cid:373)"s outer shell. Ofte(cid:374) a(cid:272)hie(cid:448)ed (cid:271)y shari(cid:374)g electrons with other atoms. The force that holds two atoms together through a pair of shared electrons. Electronegativity desire for electrons. (o = 3. 5, cl = 3. 1, n = 3. 0, na = 0. 9, h = 2. 1, etc: regardless of the bond, some like more electrons, x (cl na) = 2. 2 large. Large difference in electronegativity cl takes an electron from na (ionization ) both now satisfy octet rule: ex: nacl negatively charged chloride is attracted to positively charged sodium. The force that holds them together is an ionic bond. Very strong but not as strong as covalent: dipoles, small difference in electronegativity, oxygen steals some electron density from hydrogen, resulting charge asymmetry is a dipole, molecules with dipoles are polar, h2o l shape molecules. Hydrogen bond: oppositely charged dipoles attract, the force holding these together.