Post on 19-Jan-2016
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