Covalent Compounds

Chapter 66-1 Covalent Bonds

Covalent Bond• The sharing of electrons between atoms• Forms a molecule• To have stable (filled) orbitals

Diatomic Molecules• Formed by covalent bond between two atoms of the same element

Molecular Orbital

• The space in which the shared electrons move

Energy and Stability• Un-bonded atoms

(except noble gases) have low stability and high potential energy• Energy is released

when they form a bond

Attraction and Repulsion

• When balanced, a covalent bond forms

Bond Length

• The distance between two bonded atoms at their minimum potential energy

Bond Energy• The energy required to

break a bond• kJ/mol

Electronegativity and Covalent Bonding• Electronegativity - How much an atom attracts electrons• Atoms share electrons equally or unequally – depending on the

electronegativity of the atoms

Nonpolar Covalent Bonds

• Electrons are shared equally

Polar Covalent Bonds

• Atoms share electrons unequally• Have different

electronegativities

Dipole Molecule• One end is partial positive and the other end is partial negative• Hydrogen and fluorine

Polarity and Bond Strength• The greater the difference in electronegativity, the greater the polarity, and the

greater the bond strength

------------------ Bond Strength ------------------

Determining Bond Types• Differences in Electronegativity of the atoms

Metallic Bonds• Results from the attraction between metal atoms and the surrounding

sea of electrons

Properties of Substances Depends on Bond Type

• Metallic – good conductors• Ionic – strong bonds, high

melting point• See table 3 page 197

Drawing and Naming Molecules

Section 6-2

Valence Electrons

Lewis Electron-Dot Structures

Octet Rule

Lewis Structures Model Covalently Bonded Molecules

Unshared (lone) Pairs• Not part of the bond

Single Bond• The shared pair• Can be shown by a dash

Lewis Structures for Polyatomic ions• Ammonia Ammonium ion

enclose in brackets w/ + charge

Double Bonds

• Share 4 (2 pair) electrons• Carbon, oxygen, nitrogen

Triple Bonds

• Share 6 (3 pair) electrons• Nitrogen and Carbon

Naming Covalent Compounds

• Similar to Ionic bonds• -ide suffix

• Prefixes indicating number• On first element, only if

more than one

Molecular ShapesSection 3

Determining Molecular Shapes

• The shape helps determine the molecules physical and chemical properties

Linear Shape

• “In a line”• Molecules made

of 2 atoms• H2 or CO

VSEPR Theory

• Pronounced “vesper”• A model used to predict the shape of a molecule• Valence Shell Electron Pair Repulsion Theory• Based on the idea that valence electrons repel each other

Linear Shape

• The shared pairs repel each other and remain as far apart as possible

Bent Shape• Water H2O• Two shared pairs

and two unshared pairs• The unshared

pairs influence the shape

Tetrahedral

• Methane CH4

• Four shared pairs

Trigonal Planer

• BF3

• CH2O (Formaldehyde)• 3 shared pairs• Maximum distance apart

Trigonal Pyramidal• 3 bonding pairs, 1 lone pair• Ammonia NH3

Molecular Shapes Affects a Substance’s Properties

• Shape affects Polarity

Polarity affects Properties