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

2. 9.1 LEWIS DOT SYMBOLS
9.2 THE IONIC BOND
9.4 THE COVALENT BOND

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

5. 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.

6. 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

7. 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