HONORS CHEMISTRY Section 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 TypeMore Negative Element C-H C-S O-H Na-Cl Cs-S