Chapter 9.1 Notes
Covalent Bonds
Review
Noble gases have a very stable _____________ arrangement. Noble gases have a full
____________ energy level. This consists of ______ electrons for helium and ________
electrons for the other noble gases. Because of their stability, noble gases don’t generally
_____________ with other elements.
When a _____________ and a ___________________ react to form binary ___________
compounds, the electrons are ___________________. The resulting ions have a
______________ gas configuration, making them stable.
What is a Covalent Bond?
Sometimes atoms will _____________ electrons in order to become stable. The type of bond
where atoms share electrons is called a _______________ bond. A ______________ bond is a
type of chemical bond that results in the sharing of valence electrons. Most covalent bonds
occur between __________________ elements.
A ___________________ forms when two or more atoms bond covalently. Carbohydrates,
proteins, fats, DNA, cotton, and wool are all types of molecules.
Hydrogen (H2), nitrogen (_____), oxygen (_____), fluorine (_____), chlorine (_____), bromine
(_____), and iodine (_____) are all a specific type of molecule called a _______________
molecule. They do not exist in nature as a single molecule because the diatomic molecule
formed is more stable than the individual atoms. All the diatomic molecules share at least one
pair of valence electrons.
Single Covalent Bonds
When a ____________ pair of electrons is shared, a ____________ covalent bond forms.
Hydrogen has a single pair of shared electrons. The ____________ pair of electrons is referred
to as the _________________ pair and is represented by ________ _________ or a ________
in a Lewis structure for the molecule. The ____________ structure uses electron-dot diagrams
to show how electrons are arranged in molecules.
Single covalent bonds are also called _______________ bonds (represented by the Greek
letter sigma – σ). A sigma bond forms from the overlap of an _____ orbital with another
_____ orbital, an _____ orbital with a p orbital, or a _______ orbital with another _____
orbital.
Lewis Structures of Molecules
Example for the hydrogen molecule (H2) – each hydrogen has 1 valence electron to share – so
the molecule will have one pair of shared electrons. The Lewis structure looks like one of the
following:
1st draw each Hydrogen’s electron dot structure:
H·
and
H·
2nd put the structures together into one larger structure:
H:H
Each dot represents 1 electron
Example: H2O
Example: NH3
Example: CH4
OR
H–H
The line represents an electron pair
Multiple Covalent Bonds
Many molecules attain a ___________ gas configuration by ____________ more than one pair
of electrons between two atoms – they will form _______________ covalent bonds. The most
likely atoms to form multiple covalent bonds are as follows: _____________, _____________,
_____________________, and _________________.
__________________ and ______________ covalent bonds are examples of multiple bonds.
How many pairs of electrons are shared when a double bond forms? ___________. The atoms
of the ______________ (________) molecule share _________ pairs of electrons. Each oxygen
atom has _________ valence electrons and must obtain ________ more electrons for a noble
gas configuration. If each oxygen shares ________ electrons, then each oxygen atom will have
a full valence shell and a ______________ bond will result.
How many pairs of electrons are shared when a triple bond forms? ____________.
______________ (____) shares three electron pairs between two atoms. Each nitrogen has
_______ valence electrons and needs _________ additional electrons to attain the noble-gas
configuration. A ____________ bond occurs between two nitrogen atoms.
A __________ bond (represented by the Greek symbol pi – π) is formed when parallel orbits
overlap to share electrons. A ________________ bond consists of one __________ bond and
at least one ______ bond. A _____________ bond consists of one sigma bond and ________ pi
bond. A triple bond consists of _________ sigma bond and ________ pi bonds. A ______ bond
always accompanies a sigma bond when forming ______________ bonds.
Strength of Covalent Bonds
Some covalent bonds are ______________ more easily than others because they differ in
strength. The distance between the two bonding nuclei is called the __________ __________.
The bond length is determined by the _________ of the atoms and how many __________ are
shared. As the number of shared pairs ______________, bond length _______________ which
results in an _________________ bond strength. The shorter the bond length, the
_________________ the covalent bond.
The amount of energy required to break a specific covalent bond is called the ______________
_____________________ energy. The bond dissociation energy is always a _______________
value because breaking bonds always requires ________________ energy. The shorter the
bond length, the ________________ the bond dissociation energy.
____________________ reactions occur when a greater amount of energy is required to break
the existing bonds in the reactants than is released when the new bonds form in the products.
____________________ reactions occur when more energy is released forming new bonds
than is required to break bonds in the initial reactants.