Topic: Chemical Bonding Aim: How are covalent bonds formed, & what are properties of covalent compounds? Do Now: Explain, in terms of electrons, how an ionic bond forms between magnesium and sulfur HW:

Covalent Bonds Formed when 2 (or more) NONMETALS SHARE e- Results in a MOLECULE By sharing, they can use each other’s e- to count towards their octet

Characteristics Weaker than ionic bonds Lower m.p./b.p. than ionic cpds Can be solid, liquid, or gas at rm. temp. Soft, Poor conductors, Low mp/bp SPLash in water (which is covalent)

Example: How does H2 form? The nuclei repel each other, since they both have a positive charge, and like charges repel. + +

Example: How does H2 form? But, the nuclei are attracted to each other’s electrons (each H has 1) They share the electrons + +

Formation of a Covalent Bond

Another Example: Covalent Bonding Fluorine has seven valence electrons F

F F Covalent bonding Fluorine has seven valence electrons A second atom also has seven F F

F F Covalent bonding Fluorine has seven valence electrons A second atom also has seven By sharing electrons… F F

F F Covalent bonding Fluorine has seven valence electrons A second atom also has seven By sharing electrons… F F

F F Covalent bonding Fluorine has seven valence electrons A second atom also has seven By sharing electrons… F F

F F Covalent bonding Fluorine has seven valence electrons A second atom also has seven By sharing electrons… F F

F F Covalent bonding Fluorine has seven valence electrons A second atom also has seven By sharing electrons… F F

F F Covalent bonding …both end with full PELs Fluorine has seven valence electrons A second atom also has seven By sharing electrons… …both end with full PELs F F

F F Covalent bonding Fluorine has seven valence electrons A second atom also has seven By sharing electrons… …both end with full PELs F F 8 Valence electrons

F F Covalent bonding Fluorine has seven valence electrons A second atom also has seven By sharing electrons… …both end with full PELs F F 8 Valence electrons

Types of Covalent Bonds Nonpolar covalent Polar covalent Coordinate covalent

Nonpolar Covalent Bonds Same 2 nonmetals bonded Diatomic Molecules Br2 I2 N2 Cl2 H2 O2 F2 SHARE THEIR VALENCE e- EQUALLY!

Characteristics of Nonpolar Covalent Bonds Molecules are NOT strongly attracted to one another They can move freely and tend to exist as liquids or gases at room temperature Examples?

Polar Covalent Bond Ex. CCl4 , H2O, CO2 2 different non metals bonded THEY SHARE THEIR VALENCE e- UNEQUALLY! The valence e- are MORE LIKELY TO BE FOUND NEAR THE ATOM WITH THE HIGHER ELECTRONEGATIVITY! To ID which bond is “more polar” Find the DIFFERENCE IN ELECTRONEGATIVITY Bigger difference, more polar bond Ex: H2O, CO, PCl4

Polar Covalent Bond

Coordinate Covalent Bond When 1 atom donates both electrons that are shared Ex. NH4+ Ex. H3O+ Polyatomic ions (Table E)

Network Solids Network solids Form macromolecules Repeat same structure over and over Properties: hard, poor conductor, high m.p. Ex: diamond – no separate particles – carbon atoms connected by covalent bonds to form one big macromolecule Ex: SiC, SiO2 (silicon dioxide - sand)