Quick Review of Lecture 9 Feb. 4, 2019
Lewis Structures
Concepts and Vocabulary: Formal
Charges, Valences, Oxidation States
Resonance Structures; Hyper and
Hypovalent sites
VSEPR
, Lewis Structures
A bond between two atoms is formed by means of sharing of a pair of
electrons
Each atom shares electrons with neighbors to achieve a total of eight
valence electrons
Determine connectivity of the atoms in the molecule
Sum up the total number of valence electrons in the molecule
Distribute the electrons so that each atom acquires an octet (duet for H!)
in either
a) bonding pairs (denoted : or – ) shared between a pair of atoms, or
b) lone pairs (denoted : ) that belong to a single atom (i.e., “unused”
in making bonds and occupy more space than bonded pairs).
Examples: HF, CF4, NH3, COCl2, CO, CO2, N2O, H2CN2, N3‐, N5+
, Vocabulary and Concepts
Valence: Number of electrons an atom uses in bonding.
Oxidation State or Number: Charge on atoms according to a set of rules
That consider the electronegativity of atoms within the molecule or material.
1) In pure element, Oxidation Number = 0
2) F, the most electronegative element, in a molecule is ‐1
3) O is typically ‐2; sometimes (in peroxides), ‐1
4) Alkali metals, +1; Alkaline Earth metals, +2; Gp 3, generally +3; Transition
metals variable + charged.
5) H is +1 when combined with more electroneg. element; ‐1 when combined
with more electropositive element. Therefore, H in compound with any M is a
hydride, H‐1.
6) Summation of Ox. States must equal charge on ion; or zero if neutral molecule.
Formal Charges: Charge on atom according to equation:
F.C. = # valence electrons ‐ # of electrons in non‐bonded pairs – ½ # of electrons in bonds
Coordination number: Number of atoms bonded to the atom in question.
Parkin, G. J. Chem. Educ. 2006, 83, 791
Jensen, W. B. J. Chem. Educ. 2006, 83, 1751
Lewis Structures
Concepts and Vocabulary: Formal
Charges, Valences, Oxidation States
Resonance Structures; Hyper and
Hypovalent sites
VSEPR
, Lewis Structures
A bond between two atoms is formed by means of sharing of a pair of
electrons
Each atom shares electrons with neighbors to achieve a total of eight
valence electrons
Determine connectivity of the atoms in the molecule
Sum up the total number of valence electrons in the molecule
Distribute the electrons so that each atom acquires an octet (duet for H!)
in either
a) bonding pairs (denoted : or – ) shared between a pair of atoms, or
b) lone pairs (denoted : ) that belong to a single atom (i.e., “unused”
in making bonds and occupy more space than bonded pairs).
Examples: HF, CF4, NH3, COCl2, CO, CO2, N2O, H2CN2, N3‐, N5+
, Vocabulary and Concepts
Valence: Number of electrons an atom uses in bonding.
Oxidation State or Number: Charge on atoms according to a set of rules
That consider the electronegativity of atoms within the molecule or material.
1) In pure element, Oxidation Number = 0
2) F, the most electronegative element, in a molecule is ‐1
3) O is typically ‐2; sometimes (in peroxides), ‐1
4) Alkali metals, +1; Alkaline Earth metals, +2; Gp 3, generally +3; Transition
metals variable + charged.
5) H is +1 when combined with more electroneg. element; ‐1 when combined
with more electropositive element. Therefore, H in compound with any M is a
hydride, H‐1.
6) Summation of Ox. States must equal charge on ion; or zero if neutral molecule.
Formal Charges: Charge on atom according to equation:
F.C. = # valence electrons ‐ # of electrons in non‐bonded pairs – ½ # of electrons in bonds
Coordination number: Number of atoms bonded to the atom in question.
Parkin, G. J. Chem. Educ. 2006, 83, 791
Jensen, W. B. J. Chem. Educ. 2006, 83, 1751
