Chemical Bonding I: Basic Concepts Chapter 9 Semester 1/2016

9.1 LEWIS DOT SYMBOLS 9.2 THE IONIC BOND 9.4 THE COVALENT BOND

Valence electrons..total electrons in the outer most shell which participate in chemical bonding. Li * Example: 3Li…1s2, 2s1 valence e- = 1 4Be..1s2, 2s2 valence e- = 2

The Ionic Bond - - - Na+ F Na + F 1s2,2s22p6,3s1 1s2,2s22p5 [Ne] [Ne] Na Na+ + e- e- + F - F - Na+ + Na+ Chemical bond exists between metal and non-metal. Metal loses electron to become cation (stable, inert electron structure) Non-metal gains electron to become anion (stable, inert electron structure) Strong attraction between cation and anion produces ionic bond.

Why should two atoms share electrons? A covalent bond is a chemical bond in which two or more electrons are shared by two Non-metal atoms. Why should two atoms share electrons? 7e- 7e- 8e- 8e- F F + F Lewis structure of F2 lone pairs F single covalent bond single covalent bond F

Lewis structure of water single covalent bonds 2e- 8e- 2e- H + O + H O H or Double bond – two atoms share two pairs of electrons 8e- 8e- 8e- O C or O C double bonds Triple bond – two atoms share three pairs of electrons 8e- N 8e- or N triple bond