Covalent Bonding Covalent Bonding and Covalent Nomenclature

Covalent bonding – sharing of electrons  Made of two or more nonmetals!

Formed between two nonmetals Formed between two nonmetals Electrons are shared by the atoms Electrons are shared by the atoms Covalent Bonds

 In a covalent bond, the shared electrons are considered part of the complete outer energy level of both atoms involved.  Covalent bonding generally occurs when elements are relatively close to each other on the Periodic Table.  When two or more atoms bond covalently, a molecule is formed.

single bond shares one pair of electrons single bond shares one pair of electrons double bond shares two pairs of electrons double bond shares two pairs of electrons triple bond shares three pairs triple bond shares three pairs of electrons Covalent Bond Sharing

Covalent compound formulas  Examples: carbon dioxide, carbon tetrachloride  Oxidation Number: Unpaired Valence Electrons –Number of covalent bonds an atom can form –Hydrogen = 1 –Oxygen = 2; single and double bonds –Nitrogen = 3; single, double and triple bonds –Carbon = 4 - single, double and triple bonds

Lewis Dot Structures Hydrogen chloride formation

Lewis Dot Structures Phosphorus tribromide (PBr 3 ) formation

Properties of Covalent Molecules  Solids, liquids, or gases at room temperature  Nonconductive as solids  May dissolve in water  Dissolve in nonpolar solvents (hexane or alcohol)  Non-conductive when dissolved  Low melting points

Learning Check Indicate whether a bond between the following would be 1) Ionic2) covalent ____A. sodium and oxygen ____B. nitrogen and oxygen ____C. phosphorus and chlorine ____C. phosphorus and chlorine ____D. calcium and sulfur ____E. chlorine and bromine ____E. chlorine and bromine

Polar covalent bonds  Electrons are unequally shared.  The molecule has an area of positive charge and an area of negative charge.  Not symmetrical  Examples: H 2 O(water) and NH 3 (ammonia)

 Electrons are equally shared and there is no charge.  Symmetrical  Examples: CO 2 (carbon dioxide), CCl 4 (carbon tetrachloride), O 2 (oxygen gas) Nonpolar covalent bonds

Learning Check Identify the type of bond between the following atoms A. K-N 1) nonpolar 2) polar3) ionic B. N-O 1) nonpolar2) polar3) ionic C. Cl-Cl 1) nonpolar 2) polar3) ionic

Naming Binary Molecular Compounds Two nonmetals Name each element Name each element End the last element in -ide End the last element in -ide Add prefixes to show more than 1 atom Add prefixes to show more than 1 atom For example: Carbon dioxide CO 2

Prefixes for naming *Mono 1 * Penta5 *Di2* Hexa6 *Tri3* Hepta7 *Tetra4 * Octa8  Used to indicate multiples  Mono normally omitted –Exception: carbon monoxide

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

Learning Check A.P 2 O 5 1) phosphorus oxide 2) phosphorus pentoxide 3) diphosphorus pentoxide B.Cl 2 O 7 1) dichlorine heptoxide 2) dichlorine oxide 3) chlorine heptoxide

VSEPR Theory Valence Shell Electron Pair Repulsion

VSEPR Theory  Predicts the molecular shape of a bonded molecule  Electrons around the central atom arrange themselves as far apart from each other as possible  Unshared pairs of electrons (lone pairs) on the central atom repel the most  So only look at what is connected to the central atom

Linear  2 atoms attached to center atom  0 lone pairs  Bond angle = 180 o  Ex. : BeF 2

Trigonal Planar  3 atoms attached to center atom  0 lone pairs  Bond angle = 120 o  Ex. : AlF 3

Tetrahedral  4 atoms attached to center atom  0 lone pairs  Bond angle = o  Ex. : CH 4

Bent  2 atoms attached to center atom  2 lone pairs  Bond angle = o  Ex. : H 2 O

Metallic Bonding

Nature of Metallic Bonding  Metal atoms from lattices  The outer valence shell electrons of each metal atom contribute to a “sea” of electrons in the lattice

Metallic Properties  High thermal and electrical conductivity  Malleable- can be hammered into sheets  Ductile- can be drawn into wire