_____________ Bond Between nonmetallic elements of similar electronegativity. Formed by sharing electron pairs Stable non-ionizing particles, they are not conductors at any state FORM MOLECULES Examples; O 2, CO 2, C 2 H 6, H 2 O, SiC Bonds in all the polyatomic ions and diatomics are all covalent bonds

_____________ Chemical Bonds According to the Lewis model ionic bond –an atom may lose or gain enough electrons to acquire a filled valence shell and become an ion. An ionic bond is the result of the force of attraction between a cation and an anion. covalentbond –an atom may share electrons with one or more other atoms to acquire a filled valence shell. A covalent bond is the result of the force of attraction between two atoms with relatively close electronegativities that share one or more pairs of electrons.

Material from karentimberlake.com and H. Stephen Stoker If the difference in electronegativities is between: – 1.7 to 4.0: Ionic – 0.3 to 1.7: Polar Covalent – 0.0 to 0.3: Non-Polar Covalent Try KF, H 2 O, Cl 2 ____________ or _________ ???

C. Johannesson A. __________ of Bond Formation Potential Energy – based on position of an object – low PE = high stability

C. Johannesson Bond Energy A. Energy of Bond Formation Bond Length Bond Energy – Energy required to break a bond

C. Johannesson A. Energy of Bond Formation Bond Energy – Short bond = ____________ bond energy

Drawing ________ Structures 1. Determine the number of valence electrons in the molecule 2. Decide on the arrangement of atoms in the molecule 3. Connect the atoms by single bonds 4. Show bonding electrons as a single line; show nonbonding electrons as a pair of Lewis dots single bond double bond triple bond 5. In a single bond, atoms share one pair of electrons; in a double bond, they share two pairs, and in a triple bond they share three pairs.

Covalent Bonds Two nonmetal atoms form a covalent bond because they have less energy after they bonded H  +  H H : H = H  H = H 2 hydrogen molecule

C. Johannesson B. Lewis Structures Electron Dot Diagrams – show valence e - as dots – distribute dots like arrows in an orbital diagram – 4 sides = 1 s-orbital, 3 p-orbitals – EX: oxygen X

C. Johannesson B. Lewis Structures Octet Rule – Most atoms form bonds in order to obtain 8 valence e - – Full energy level stability ~ Noble Gases Ne

Double Covalent Bond 2 pairs of electrons are shared between 2 atoms Example O 2

Triple Covalent Bond 3 pairs of electrons are shared between 2 atoms Example N 2

Lewis Structures Other molecules having single covalent bonds H 2 O The hydrogens share their electrons w/ oxygen so that O has 8 e- and each H has 2 e-

Covalent Bonds in NH 3

Learning Check Examples –draw a Lewis structure for hydrogen peroxide, H 2 O 2 –draw a Lewis structure for methanol, CH 3 OH –draw a Lewis structure for acetic acid, CH 3 COOH

C. Johannesson C. Molecular Nomenclature Prefix System (binary compounds) 1.Less e - neg atom comes first. 2.Add prefixes to indicate # of atoms. Omit mono- prefix on first element. 3.Change the ending of the second element to -ide.

C. Johannesson PREFIX mono- di- tri- tetra- penta- hexa- hepta- octa- nona- deca- NUMBER C. Molecular Nomenclature

C. Johannesson zCCl 4 zN 2 O zSF 6 C. Molecular Nomenclature

C. Johannesson zarsenic trichloride zdinitrogen pentoxide ztetraphosphorus decoxide C. Molecular Nomenclature

C. Johannesson NOF Cl Br I H C. Molecular Nomenclature The Seven Diatomic Elements Br 2 I 2 N 2 Cl 2 H 2 O 2 F 2

Material from karentimberlake.com and H. Stephen Stoker __________ Elements Elements that are naturally in molecules with 2 atoms each. “H NO Halogens” Existing as diatomic molecule yields a stable octet Gases that exist as diatomic molecules are H 2, F 2, N 2, O 2, Cl 2, Br 2, I 2 Examples Fluorine & Bromine

Material from karentimberlake.com and H. Stephen Stoker Common Names:

Learning Check Fill in the blanks to complete the following names of covalent compounds. CO carbon ______oxide CO 2 carbon _______________ PCl 3 phosphorus _______chloride CCl 4 carbon ________chloride N 2 O_____nitrogen _____oxide © Karen Timberlake

Material from karentimberlake.com and H. Stephen Stoker Learning Check A.P 2 O 5 B.Cl 2 O 7 C. Cl 2

Bond Polarity: Polar Polar covalent bond Electrons are shared between different nonmetal atoms Due to differing electronegativities, some elements will hold the e- more tightly than the other in a covalent bond, therefore one side of the molecule is partially (+) and one side of the molecule is partially (-). Examples: Cl 2 O SOCl 3 N

Material from karentimberlake.com and H. Stephen Stoker

Material from karentimberlake.com and H. Stephen Stoker Chemical Bonding: The Covalent Bond Model ← Fig (a) In the nonpolar covalent bond present, there is a symmetrical distribution of electron density. (b) In the polar covalent bond present, electron density is displaced because of its electronegativity.

C. Johannesson ++ -- ++ B. Lewis Structures ____________ Covalent - no charges _________ Covalent - partial charges

Chemical Bonding: The Covalent Bond Model Fig (a) Methane is a nonpolar tetrahedral molecule. (b) Methyl chloride is a polar tetrahedral molecule.

- water is a polar molecule because oxygen is more electronegative than hydrogen, and therefore electrons are pulled closer to oxygen.

C. Johannesson IONIC COVALENT Bond Formation Type of Structure Solubility in Water Electrical Conductivity Other Properties e - are transferred from metal to nonmetal high yes (solution or liquid) yes e - are shared between two nonmetals low no usually not Melting Point crystal lattice true molecules B. Types of Bonds Physical State solid liquid or gas odorous