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