Covalent Bonding . Sharing of Electron Pairs: Non-metal with Non-metal Atoms. Covalent Bonding . Compounds that are NOT held together by an electrical attraction, but instead by a sharing of electrons. Occur between nonmetal atoms with electronegativity differences less than 1.67.
Sharing of Electron Pairs:
Non-metal with Non-metal Atoms
A neutral group of atoms joined together by covalent bonds is called a molecule. A compound composed of molecules is called a molecular compound.
The chemical formula for a molecule is called the molecular formula.
Properties of Molecular Compounds:
Do not conduct electricity. They form nonelectrolytes.
Molecular compounds tend to have lower melting and boiling points than do ionic compounds.
Dispersion forces - caused by motion of electrons (weakest intermolecular force). More electrons = stronger dispersion forces. Diatomic halide molecules are held together by dispersion forces.
Weak bonds between bonded hydrogen and some electron dense species. (F,O,N)
Polar bonds have more electrons on one side of the bond than the other. Electrons concentrate around electronegative elements.
Polar molecules have polar bonds. A molecule with two poles is called a dipole.
Determine total number of valence electrons
Based on usual bond numbers, identify reasonable layout for atoms <VSEPR>
Place bonding electrons between atoms to make usual number of bonds
Place remaining electrons as lone pairs around atoms still lacking an octet
H + C Final Structure: Tetrahedral
H + N Final Structure: Trigonal Pyramidal
H + O Final Structure: Bent
H + F Final Structure: Linear
Patterns for Major Elements:
1 Lone Pair
2 Lone Pairs
3 Lone pairs
Other Compounds Have Same Pattern:
S (like Oxygen) = 2 bonds, 2 lone pairs
C = 4 bonds; O = 2 bonds, 2 lone pairs
4 Bonds, each carbon
Two bonds at oxygen
Total valence e-= 16 (Oxygen = 6 e-, each;
Carbon = 4 e-. Four bonds/C; 2 bonds oxygen
Total valence e- = 10 (H = 1, C = 4, N = 5)
Bonds: C = 4, N = 3, H = 1
Total valence e- = 18 (O = 6, Cl = 7, P = 5)
Bonds: Cl = 1, P = 3, O = 2