Chemical Bonding—Intramolecular forces Ionic and Covalent Bonding

Ionic Bonding Metal and Nonmetal

Electron transfer between atoms, ELECTRON STEALING

ION formation (cation, anion) Opposite charges attract and hold atoms together Ions attracted to neighbords, not just one ion

Ionic Bonds— Attractive electrostatic forces connecting cations

and anions

Ionic Bonding--Crystals Interactions among ions lead to a patterned

arrangement of cations and anions that repeats, CRYSTAL

What is a diamond really? (diamond lattice)

Ionic Bonds

Between atoms of metals and nonmetals with very different electronegativity Huge difference in electronegativity Electronegativity value > 1.7

Form between elements located on opposite sides of the periodic table

Ionic Bonds (cont.) Conductors

High melting point.

Water soluble

Crystallize (form crystals)

Examples; NaCl, CaCl2, K2O

Ionic Bonds: One Big Greedy Thief Dog!

Example 1: NaCl

Example 2: CaO

Example 3: K2O You Try !

Covalent Bonding ELECTRON SHARING between 2 atoms (nonmetals)

Formation of MOLECULES

Small difference in electronegativity

Bonding pairs— Electron pairs shared between atoms

Nonbonding/lone pairs— Unshared electrons, “lone wolves” Only reside around one atom

Covalent Bonding continued….

Between nonmetallic elements of similar electronegativity. Small electronegativity difference <1.7

Formed between elements on the same side of the periodic table.

Example 1: Cl2

Example 2: H2O

Multiple Bonds Single bonds—

1 electron pair shared between atoms

Double bonds— 2 electron pairs shared between atoms

Triple bonds— 3 electron pairs shared between atoms

Example 1: CO2

Example 2: N2

Covalent Bonding and Polarity

What is polarity? Focus on covalent bonds

Contributes to the properties of chemical compounds

Based on electronegativity difference between atoms within chemical bonds

Electronegativity and Bond Polarity

Covalent Bond Polar Covalent Ionic Bond

(0—0.5) (0.5—1.9) (1.9—3.5)

Chose your polarity 1) Nonpolar Covalent

small to same electronegativity difference Occurs among same or similar atoms bonded together EQUAL sharing of electrons, equal distribution of

electron density

2) Polar Covalent difference in electronegativity Most electronegative atom pulls electrons towards it UNEQUAL sharing of electrons, electron density

displaced toward electronegative atom

Polar Covalent Bonds

Example 1: Arrange the following

bonds in order of DECREASING polarity. Br—Cl H--Cl Cl—Cl I--Cl Cl--F

Partial Charges Exist in polar covalent molecules

Demonstrates tendency of one end to be “slightly” negative or positive

NO charge on the whole molecule

Example 1: H2O

Example 2: PH3

Homework

Chemical Bonding I Worksheet