Covalent Compounds
Chapter 6
6-1 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
• Atoms share
electrons unequally
• Have different
electronegativities
Polar Covalent Bonds
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
ElectronDot
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 Shapes
Section 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