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CHAPTER 8
Section 2- Compounds, Chemical Formulas, and
Covalent bonds
COMPOUNDS
Compounds- a substance made up of two or
more elements
 The compound has different properties from
the elements that make up the compound
 Ex- NaCl- common table salt

Na- Is a bright, soft metal when it is purifies
 Cl- is a gas at room temperature
 However, when combined they make a compound
that is used as a seasoning for foods.

CHEMICAL BONDS
A chemical bond is a force that joins atoms
together
 Bonds can be formed in two ways

Sharing electrons (Covalent bonds)
 Giving/Receiving electrons (Ionic Bonds)

COVALENT BOND

A covalent bond is a chemical bond formed when
two atoms share one or more pairs of valence
electrons
Generally non metals form these kinds of bonds
 Each element in the bond wants to reach noble gas
status
 Each element wants to share electrons so that each
has 8

NUMBERS OF COVALENT BONDS
A single covalent bond occurs when two atoms
share one pair of valence electrons
 A double covalent bond occurs when two atoms
share two pairs of valence electrons
 A triple covalent bond occurs when two atoms
share three pairs of covalent bonds

Strength of bonds
 Strongest- Triple
 Weakest-Single

COVALENT COMPOUNDS

The bonds in water, carbon dioxide, and sugar
are very different but they do have some
similarities
Low melting and boiling points
 Usually gases or liquids at room temperature
 Poor conductors of thermal energy and electricity

MOLECULES
The chemically stable unit of a covalent
compound is a molecule
 A molecule- is a group of atoms held together by
covalent bonding that acts as a single or
independent unit
 For example- Table sugar is C₁₂H₂₂O₁₁

One grain of sugar is made up of millions of sugar molecules
 One molecule would be made up of 12 Carbon atoms, 22
Hydrogen atoms, and 11 Oxygen atoms

WATER AND OTHER POLAR MOLECULES
In a covalent bond, one atom can attract the
other atom more strongly
 For example, in water the Oxygen attracts the
Hydrogen more
 The Oxygen is more negative and has a partial
negative charge
 The Hydrogen has a partial positive charge
 A molecule that has a partial negative and a
partial positive charge because of unequal
sharing of electrons is POLAR COVALENT

NONPOLAR MOLECULES
Usually occurs when the same atom is bonded
with itself
 Also occurs when the electrons are shared
equally
 Non polar compounds dissolve easily in other non
polar compounds but not so well in polar
compounds
 “Like dissolves like”

CHEMICAL FORMULAS AND MOLECULAR
MODELS
A chemical formula is a group of chemical
symbols and numbers that represent elements
and the number of atoms of each element.
 “like a recipe”
 CO₂ means one atom of carbon and 2 atoms of oxygen
 The subscripts shows the quantity of the element
 The formula DOES NOT SHOW THE SHAPE OF THE
MOLECULE
