After today, you will be able to… Explain how ionic and covalent bonding occurs Write dot diagrams for elements in the s and p blocks Determine the number of valence electrons in a particular atom

Unit: Chemical Bonding Day 1 - Notes Unit: Chemical Bonding The Basics of Chemical Bonding

Two types of bonding: Ionic Bonding: Involves a transfer of electrons. One element loses electrons and the other gains electrons. Covalent Bonding: Involves a sharing of electrons. Atoms will share in order to reach a stable electron configuration.

The Octet Rule Atoms will gain or lose enough electrons to make them isoelectronic with a noble gas. -Except for H and He, there will be 8 electrons in their valence shell

Electron Dot Structures A way to show the number of valence electrons in an atom Valence electrons must be labeled like this: X 5 2 3 1 6 8 4 7

The number of valence electrons can be determined by the group the elements are in – s and p blocks only! Group # 1 2 13 14 15 16 17 18 Valence E- E- Dot Strux 1 2 3 4 5 6 7 8

Valence electrons determine chemical reactivity – elements in the same group behave the same! 1 2 13 14 15 16 17 18 Electron activity Charge Group # Lose/ Gain 4 Lose 1 Lose 2 Lose 3 Gain 3 Gain 2 Gain 1  +/- 4 Gain 1 X +1 +2 +3 -3 -2 -1 

Review: E- Configurations for Ions Examples: Mg+2 = P-3 = 1s2 2s2 2p6 = [Ne] 1s2 2s2 2p6 3s2 3p6 = [Ar]

Introduction to Ionic Bonding An ionic bond forms from the attraction between + and – ions. An ionic compound is made up of crystals A crystal consists of a 3D, repeating pattern of alternating + and – ions Formula unit: the lowest whole number ratio of ions Ionic compounds have high melting points Conduct electricity when melted or dissolved Example: NaCl