Covalent Compounds Chapter 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 Structure s

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 H 2 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 H 2 O Two shared pairs and two unshared pairs The unshared pairs influence the shape

Tetrahedral Methane CH 4 Four shared pairs

Trigonal Planer BF 3 CH 2 O (Formaldehyde) 3 shared pairs Maximum distance apart

Trigonal Pyramidal 3 bonding pairs, 1 lone pair Ammonia NH 3

Molecular Shapes Affects a Substance’s Properties Shape affects Polarity

Polarity affects Properties