Bell ringer 2 nd period (Molly, Timmy)(Kiersten, Michael)(Caitlin, John)(Kaitlyn, Ariel)( Morgan, Sherman) (Cheyenne, Emily)(Racheal, Courtney M)(Jenna, Courtney L) 8 th period (Kaitlyn, Destanie)(Tim, Morgan)(Jen, Chelsey) (William, Hannah)

Electronegativity Electronegativity: is a chemical property that describes the ability of an atom to attract electrons (or electron density) towards itself Electronegative atoms love electrons

Polar bonds Polar covalent bonds are: When electrons between two atoms are not shared equally Nonpolar covalent bonds are: When electrons between two atoms are shared equally

Polar examples HCl H 2 O

How to tell if something is polar Use electronegativity the difference in electronegativity will tell you how polar a bond is. E.g.HF F 2

Bell ringer List the following bonds in order of polarity? HFHClHBr NaF

Polarity Polar molecules are: Molecules that have one end of the molecule more slightly negative then its other end. A molecule that has two poles are called Dipoles Not all molecules with polar bonds are polar molecules

Nonpolar examples CCl 4 CO 2

Intermolecular forces Intermolecular forces are attractions between molecules that are weaker than ionic and covalent bonds There are several different types of these forces. Two main types are van der Waals forces and hydrogen bonds

Van der Waals Van der Waals forces are named after a Dutch chemistry. There are two types of van der Waals forces, Dispersion forces, and dipole interactions. Dispersion forces are the weakest of all molecular forces and are caused by the motion of the electrons.

Dipole interactions These occur when polar molecules are attracted to each other. The positives will be attracted to the negatives and negatives will be attracted to the positives

Hydrogen bonds When a hydrogen is bonded covalently to a very electronegative atom it leaves its protons unshielded. These protons will then from small bonds with lone pairs of electrons on a nearby atom.

Other Lewis stuctures The most common way to draw Lewis structures is with dots but there is a different way. A bonding pair of electrons can be represented by a line (-) : = - E.g. NH 3 CH 3 OH

Practice using lines instead of dots for the following Lewis structures. HFCCl 4 C 2 H 4