Bonding

Valence Electrons• In the highest energy level • Determine chemical properties. • Elements bond to get 8 valence e- (octet rule)

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Anions, Cations, and Electron Configuration

Cations form by losing valance electrons to take on a noble gas configuration (ns2np6)

Anions, Cations, and Electron Configuration

Cations form by losing valance electrons to take on a noble gas configuration (ns2np6)

So Li loses the 2s1 electron to form Li+1.

Mg loses both 3s2 electrons to form Mg+2

Al loses three electrons from 3s23p1 to form Al+3

Anions, Cations, and Electron Configuration

Anions form by gaining valance electrons to take on a noble gas configuration (ns2np6)

So F becomes F1- by gaining a 2p electron to have the new valance configuration 2s22p6. S becomes S2- by gaining two 2p electrons to have the new valance configuration 3s23p6. N becomes N3- by gaining three 2p electrons to have the new valance configuration 2s22p6.

Ionic Compounds• Made of metal cations (+) and nonmetal anions (-)

• Have no charge

• Solid at room temperature

• High melting points

• Conduct electric current when dissolved in water

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Na+ Cl-

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Writing Ionic Formulas

1. Write each ion with the correct charge (cations first!)

2. Bring the charge # (NOT the + or -) down as a subscript and switch which element it goes to

Aluminum and oxygen

Al3+ O2-

Al2O3

Naming Ionic Compounds

• Name of the cation– Roman numeral for cations with mutliple + charges

• Name the anion– ide is single anion– -ate or -ite is polyatomic

CaF2

Li3PO4

PbS2

Calcium fluoride

Lithium phosphate

Lead (IV) sufide

Covalent Bonds1. Nonmetal atoms are held

together by sharing electrons2. low melting and boiling point3. All phases at room temperature

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Diatomic Molecules

H2, N2, O2, F2, Cl2, Br2, I2, At2

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Naming and Writing Formulas for Covalent Compounds

Indicate # of each atom using prefixes (mono, di, tri, tetra, penta, hexa, hepta, octa, nona, deca)

The first element does not use mono if there’s only one.

NO2

P2O4

nitrogen dioxide

diphosphorus tetroxide

Lewis Structures

Step 1: Set up the following table to determine bond numbers

Atom V-Electrons

# Needed

S

O

O

O

Total

Step 2: Connect atoms based on bond numbers calculated

Step 3: Fill octets with unshared electrons

VSEPR THEORY

Valence

Shell

Electron

Pair

Repulsion

. .

. .

tetrahedaral

Trig planar

linear

bent

Trig pyramid