Bell Ringer 4-21-09 Period # tell you _____________________. Group # tells you _____________________. Draw an electron dot diagram for Br (Bromine). What is the octet rule? Show how these two atoms bond: Ca + Se 

Bell Ringer 10-26-09 An ionic bond is a transfer of ________. If an element gives up an electron, its charge is _______. If an atom takes an electron, its charge is _______. For an atom to be happy, it needs ______ electrons in its outer energy level (with the exception of He). Draw an electron dot diagram for Si (Silicon).

ALCOS Objectives # 2 Describe the structure of atoms. # 5 Differentiate between ionic and covalent bonds.

Covalent bonds Chapter 5 Section 3

“Co” = together, or sharing Covalent Bonds “Co” = together, or sharing A covalent bond involves a SHARING of electrons.

Recall that ionic bonds usually form between a metal and a nonmetal. Covalent Bonds usually form between nonmetals. Recall that ionic bonds usually form between a metal and a nonmetal.

Molecule A molecule is a NEUTRAL group of atoms joined by covalent bonds.

Water H O H

Double and Triple Bonds Double bond- chemical bond formed when atoms share two electrons O O O C O Triple bond- chemical bond formed when atoms share three electrons N N

Properties of covalent bonds Low melting points Low boiling points Do NOT conduct electricity when dissolved in water

Covalent Bond

Two types of covalent molecules

Unequal Sharing of Electrons In a covalent bond, atoms of some elements pull more strongly on shared electrons than do atoms of other elements.

Polar and Nonpolar covalent bonds Polar- Unequal sharing of electrons H F Nonpolar – EQUAL sharing of electrons F F