1. Chemical Bonding Notes

2. Valence electrons are used in bonding.
Stable elements want to achieve 8 electrons similar to the noble gases
A metal wants to achieve the configuration for the noble gas before.
A nonmetal wants to achieve the configuration for the noble gas after.

3. Bond- force that holds groups of two or more atoms together and makes them function as a unit
Bond energy- energy required to break the bond (tells the bond strength)
Ionic bonding- between ionic compounds which contain a metal and a nonmetal
Atoms that lose electrons relatively easily react with an atom that has a high affinity for electrons
Transfer of electrons
Covalent bonding- between two nonmetals
Electrons are shared by nuclei
Polar Covalent bonding- unequal sharing of electrons
positive end attracted to the negative end
(delta) indicates partial charge

4. Electronegativity difference
Electronegativity-(p. 402) relative ability of an atom in a molecule to attract shared electrons to itself
The higher the atom’s electronegativity value, the closer the shared electrons tend to be to that atom when it forms a covalent bond
Increases – across a period
Decreases- down a group
Electronegativity difference
Bond type
Zero ( )
Covalent
Intermediate
(0.4 – 1.4)
Polar covalent
Large (>1.4)
Ionic

5. Bond Type Ex. Determine if each bond is covalent, polar covalent or ionic.
H-H, O-H, Cl-H, S-H, F-H
H-H = = 0 covalent
O-H = = 1.4 polar covalent
Cl-H = = .9 polar covalent
S-H = = .4 covalent
F-H = = 1.9 ionic

6. Naming Molecular Compounds Prefixes: (MEMORIZE)
Molecule (molecular compound) – term used to describe covalent compounds, made from two nonmetals
Naming Molecular Compounds
Prefixes: (MEMORIZE)
Mono-1 tetra-4 hepta-7 deca-10
di-2 penta-5 octa-8
tri-3 hexa-6 non-9
prefixes are used with both the first named and second named element. Exception: mono- is not used on the first word
second word ends in –ide
If a two syllable prefix ends in a vowel, the vowel is dropped before the prefix is attached to a word beginning with a vowel
monooxide
Writing Molecular Formulas
Translate prefixes

7. Molecule Names & Formulas Examples:
N2O dihydrogen monoxide
Si8O5 tetrasulfur hexachloride
NH3 carbon monoxide
P3I10 carbon dioxide =
Dinitrogen monoxide =
H2O =
Octasilicon pentoxide =
S4Cl6 =
Nitrogen trihydride = CO =
Triphosphorus deciodide =
CO2

8. Lewis Structure- representation of a molecule
Shows how the valence electrons are arranged among the atoms in the molecule. s
pz X px py • •
For an element:
Oxygen
1s22s22p4 • • O • •
For a compound: Li + Cl 
[Li]+1 + [ Cl ]-1
For a molecule:
F F •

9. Octet rule- eight electrons needed for a full, stable valence shell
Duet rule- He & He only need 2 electrons for a full, stable valence shell
Octet rule- eight electrons needed for a full, stable valence shell
Bonding pair- electrons shared with other atom
Lone pair - not involved in bonding
Line (─) = 2 shared electrons
dots (••) = 2 unshared electrons

10. Br Ge • Ex. GeBr4 5 Steps for Covalently Bonded Lewis Structures
Count to total number of valence electrons.
Arrange the atoms (least electronegative in center – except H & O)
Give each atom a single bond to the center atom
Distribute the remaining electrons from the total as lone PAIRS
Check that each atom meets the octet rule
Exceptions: Be – only 4e- , B – only 6e-, P – up to 10e-, S – up to 12e-
Not meeting to octet rule? move a lone pair to create a double bond.
Still not meeting the octet rule? move a second lone pair to create a triple bond. • Ge Br
Ex. GeBr4
Valence = 1(4) + 4(7) = 32

11. C H C H C H Single bond- involves two atoms sharing one pair
Double bond- involves two atoms sharing two pairs
Triple bond- involves two atoms sharing three pairs
Ex. CH4 C2H C2H2
Valence: 1(4) + 4(1) = 8
Valence: 2(4) + 4(1) = 12
Valence: 2(4) + 2(1) = 10 C H C H C H

12. Resonance- more than one Lewis structure can be drawn for the molecule
Ex. CO2 C O •
Valence:1(4) + 2(6) = 16 C O • C O •