Covalent Bonds: Notes 5-3

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Key Ideas:1. What holds covalently boned atoms together? 2. What are the properties of molecular compounds? 3. How does unequal sharing of electrons affect molecules?

COVALENT BONDA force that bonds two atoms together by a sharing of electrons

Each pair of shared electrons creates a bond

Usually occurs between atoms of non-metals

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Example – Water (H2O)

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OH H

How Covalent Bonds Form

How Covalent Bonds Form The oxygen atom in water and the nitrogen atom in

ammonia each have eight valence electrons as a result of forming covalent bonds with hydrogen atoms.

How Covalent Bonds FormDouble and triple bonds can form when

atoms share more than one pair of valence electrons.

Types of Covalent Bonds Different covalent bond types share a

different number of valence electrons

Single Bonds Share 2 Electrons

Double Bonds Share 4

Electrons

Triple Bonds Share 6

Electrons

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Water (H2O) Carbon Dioxide (CO2) Nitrogen (N2)

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Unequal Sharing : Polar Covalent Bond

The unequal sharing of valence electrons between two atoms that gives rise to negative and positive regions of electric charge

Results from an atom’s electronegativity – the ability to attract electrons to itself

A molecule in which the polar covalent bonds does not cancel out will be polar.

Why do you think the two Hydrogen atoms shareequally, but the Hydrogen and fluorine do not?

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Bonded hydrogen atoms showing equal sharing of

electrons

Hydrogen and fluorine bond with

an unequal sharing of electrons

ElectronCloud

Unequal Sharing of Valence Electrons Versus Equal Sharing

Fluorine forms a nonpolar bond with another fluorine atom.

In hydrogen fluoride, fluorine attracts electrons more strongly than hydrogen does, so the bond formed is polar.

A covalent bond is called nonpolar if the atoms equally share one or more pairs of electrons

Unequal (Polar) Versus Equal (Nonpolar) Sharing of ElectronsA water molecule is a polar molecule because of its bent shape.

A carbon dioxide molecule is a nonpolar molecule because of its straight-line shape.

Results of BondingMolecule

A neutral group of two or more non-metal atoms held together by covalent bonds

Type:

Diatomic - molecules consisting of two atoms of the same element bonded together

Examples:H2, F2, O2, N2

Compound A pure substance

composed of two or more different elements (atoms) that are chemically combined

Examples:CO, NO2, NaCl

Molecule, Compound, or Both?

H2

Hydrogen

NO2

Nitrogen Dioxide

Cl2

Chlorine

O2

Oxygen

NO

Nitric Oxide

CO2

Carbon Dioxide

N2

Nitrogen

H2O

Water

CH4

Methane