Chemical Bonding Chemical Bonding Chemical Bonding: Atoms will interact to combine and form new substances. Atoms that interact in this way are said to be chemically "bonded". Valence electrons determine the formation of chemical bonds. Atoms will gain or lose electrons in order to become more stable. Atoms with eight valence electrons are the most stable, the “Octet Rule.”

Covalent Bonds A. Covalent Bonds 1. Covalent bonds – valence electrons are shared between atoms. Bond between two non-metals. a. Atoms that do not lose electrons easily but attract electrons, usually form covalent bonds. b. The positive nucleus of both atoms has an equal attraction for the electrons being shared. c. The shared electrons spend most of their time between the two atoms. d. It is the attraction between the nucleus and the shared electrons that holds the atoms together. Covalent Bonds

Covalent Lewis Dots Covalent chemical bonds involve the sharing of a pair of valence electrons by two non-metal atoms. Lewis Dot diagrams show covalent bonding.

Lewis Dot Structures    

LEWIS DOT STRUCTURES (Get PT that tells you valence e-) In a Lewis dot structure, the inner full shells of electrons can be considered as included in the chemical symbol for the element, and the outer shell or valence electrons are represented by dots. The dots are placed in four groups of one or two electrons each, with 8 electrons “Octet Rule” representing a closed shell or noble gas configuration. 1 2 13 14 15 16 17 18

LEWIS DOT STRUCTURE RULES FOR COVALENT COMPOUNDS 1.  Count the total number of valence electrons for each atom in the compound. (ex. H2O = a total of 8 valence electrons, O = 6, H = 1, H = 1 for a total of 8) Count the total number of valence electrons for CO2 2.  Calculate the total number of electrons that would be needed if each atom had satisfied the Octet Rule. (O = 8, H = 2, H = 2, for a total of 12) Count the total number of electrons to satisfy Octet for CO2

3. Calculate the number of bonding electrons by subtracting the 3. Calculate the number of bonding electrons by subtracting the number in step 1 from the number in step 2.(12 – 8 = 4 total bonding electrons then divide by 2 to get your bonding pairs = 2 bonding pairs) A line joining two atoms represents a pair of electrons shared between two atoms. Dots placed next to an atom represent nonbonding electrons. Count the total number of bonding electrons for CO2 4. Place the atom that wants the most bonds in the "center". This will usually be the least electronegative element (The exception is Hydrogen, it never goes in the center.) Or the element the compound starts with. This is called the skeleton of the structure. 5. Place atoms and connect with single bonds. A single bond is between one pair (2) of electrons.

6. Place e– on outer atoms to satisfy octet rule for each of these 6. Place e– on outer atoms to satisfy octet rule for each of these atoms. Once outer atoms have satisfied the octet rule, place the left over electrons on the center atom or create double or triple bonds. 7. Create multiple bonds between outer and central atoms as necessary to satisfy octet rule by moving lone pairs to make bonding pairs. 8. Multiple Bonds are either a (double bond is between two pair of (4) electrons) or (A triple bond is between three pair of (6) electrons.) LET’S SEE WHAT THE LEWIS DOT STRUCTURES LOOK LIKE FOR H2O and CO2

TRY THESE 1. H2 2. O2 3. N2 4. CH4 5. NH3

Non-metal + Non-metal Naming Binary Non-metal + Non-meatal Nomenclature Numerical Prefixes First - write the name of the first element. Name does not change. If there is a subscript (# of atoms) add the prefix in front of the element name. The only prefix that does not apply to first element is (mono-). Do not use (mono-) on first element. Then - write the name of the second element with the prefix that corresponds to the subscript equaling the number of atoms. Finally - the second element takes on an -ide ending. PREFIX NUMBER OF ATOMS Mono- 1 Di- 2 Tri- 3 Tetra- 4 Penta- 5 Hexa- 6 Hepta- 7 Octa- 8 Nona- 9 Deca- 10 Non-metal + Non-metal Naming TRY THESE: CCl4 SF6 P2O5 PCl7 N6Br8 = Carbon Tetrachloride Examples: CO2 CO N2F S4Cl6 = Sulfur Hexafluoride = Carbon Dioxide = Phosphorous Pentoxide = Carbon Monoxide = Phosphorous Heptachloride = Dinitrogen Monofluoride = Hexanitrogen Octabromide = Tetrasulfur Hexachloride