HONORS CHEMISTRYSection 6.1 – Introduction to Chemical Bonding

Chemical Bonding Objectives Define chemical bond Explain why most atoms form chemical

bonds and the ideas behind electronegativity

Describe covalent and ionic bonding

Bonding

Holds atoms together in compounds It is a mutual electrical attraction

between: Nuclei Valence Electrons

Why? Lower Potential Energy Greater Stability

Formation of a Bond

Types of Bonds

Ionic – attraction between cations and anions Results from exchange of valence electrons

Covalent – sharing of valence electrons Polar Non-polar

Comparison of Ionic vs. Covalent Bonding

The Reality of Bonding

Usually not purely ionic or covalent Not perfectly equal sharing of electrons Not total exchange of electrons

Electrons equally shared – non-polar covalent

Electrons not equally shared – polar covalent

Electrons mostly or exclusively around one atom - ionic

Determined by electronegativity difference

Electronegativity and Bonding

Video

Ionic Character

If you have > 50% Ionic Character the Bond is Ionic (∆ electronegativity > 1.7)

If you have < 50% Ionic Character the Bond is Covalent (∆ electronegativity 1.7 or less) If you have < 5% Ionic Character the Bond is

Non-Polar Covalent (∆ electronegativity is < 0.3) If you have between 5% and 50% Ionic Character

the bond is Polar Covalent (∆ electronegativity is > 0.3 and < 1.7)

Polar vs. Non-polar

Video

Bonding

HCl Cl – H = 3.0 – 2.1 = 0.9 Polar Covalent Bond H – electrons are further away

δ+

Cl – electrons are closer δ-

Practice

Elements

∆ Electronegativity Bond Type More Negative Element

C-H

C-S

O-H

Na-Cl

Cs-S