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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