chemistry

Topics: Covalent bond, Atom, Chemical bond Pages: 35 (627 words) Published: October 1, 2014
Chapter 4 - Chemical Bonding
Outline
• 4.2 Naming Compounds and Writing
Formulas
• 4.1 Types of Chemical Bonds
• 4.4 Electronegativity, Unequal Sharing,
and Polar Bonds
• 4.5 Vibrating Bonds and the Greenhouse Effect
• 4.3 Lewis Structures
• 4.6 Resonance
• 4.7 Formal Charge: Choosing among Lewis Structures
• 4.8 Exceptions to the Octet Rule
• 4.9 The Lengths and Strengths of Covalent Bonds
© 2014 W. W. Norton Co., Inc.

1

Chemical Bonds
All chemical bonds consist of _______ that hold groups of
atoms together and make them function as a unit.

A bond will form if the energy of the aggregate is ______than that of the separated atoms.
____________ – energy required to break a chemical bond

Bonding involves ________________.

2

Chemical Bonds, cont.
In general, there are three types of chemical bonds:
I. Ionic bond: Transfer of electrons from one atom

to another. Seen primarily in M + NM. Bond is an
electrostatic attraction of of a _______for an ______.
II. Covalent bond: Results from a ________ of

outermost electrons.
A. __________covalent: ______ sharing of
electrons. Observed in two of the same NM’s
or in C-H bonds.
B. ______covalent: ________ sharing of electrons.
Observed in two different NM’s (not C-H bonds)
III. Metallic bond: Chemical bond consisting of the

unequal

nuclei of metal atoms surrounded by a “____” of
shared electrons
detailed discussion to follow …

3

Electronegativity and Types of Bonds
Q: Why do we see the different types of bonding?
A: Electronegativity difference.
Electronegativity (EN) is:
• The ability of an atom in a molecule to attract _________ in a bond to itself.
• Has values ranging from 4.0 for fluorine (the ______
electronegative) to 0.7 for cesium and francium (the
______ electronegative).
• The __________ in EN between two atoms determines
what kind of bond will form:
Ionic, Nonpolar covalent, or Polar covalent
4

Electronegativity Trends
Electronegativity increases moving ____ and to the _______
in the periodic table (omitting noble gases).
The most
electronegative
elements are F, O, N,
and Cl.

We can predict the
type of bond between
two atoms using the
EN scale below:
≤ 0.4
NonPolar covalent
>0.4 – 2.0 Polar covalent
>2.0
Ionic
5

Ionization Energies and Electronegativity
In general, periodic trends in electronegativity parallel the trend in ionization energy.

EN: __________ across a row;

__________ down a column.
6

A Deeper Look . . .
I. Ionic Bonding
• Results when a ______ reacts with a _________.
• Electrons are transferred from the metal to the nonmetal resulting in the formation of a ______ and an ______.
• Metals _____ electrons and nonmetals _____ electrons in such a way as to achieve a noble gas electron configuration, known as the “octet rule” (8e– in outermost shell)

Li+ = [He]

F– = [Ne]

• The resulting bond is due to the ____________ attraction between oppositely charged ions.
• The simplest whole-number ratio of cations to anions that yields a neutral compound is called the ____________.

7

Molecular Compounds – Covalent Bonding
• Molecular compounds are substances formed when __________ combine by ________ electrons to form covalent bonds.
• The atoms combine to form discrete molecules in such a way as each atom attains a noble gas configuration (surrounded by 8 e–). • The distance between the atoms when energy is at a minimum is called the ____________.

Electrostatic
Potential
Energy
Diagram

8

Two types of covalent bonding:
A. NonPolar Covalent Bonds
• _______ sharing of bonding pair of electrons between atoms • Results in ______ distribution of charge

• Observed in two of the ______ NM’s (as seen below for Br2) or in _____ bonds.

Br

Br

More
examples:
N2, O2, CH4

9

Allotropes – nonpolar covalent bonding
Different molecular forms of the same element
• Carbon: diamond / graphite / “buckyballs”

• Oxygen: O2...
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