Chapter 6.1
Elements combine to form
compounds
Definition of Compound
• A substance made up of atoms of two or
more different elements.
The Elements of a periodic table:
• Can form millions of
compounds
• Atoms of different
elements are held
together by chemical
bonds.
Chemical Bonds
• Can hold atoms together in large networks
or small groups
• Help determine the properties of a
compound.
The properties of a compound
depend on:
• which atoms the compound contains
• how the atoms are arranged
The properties of a compound are often
very different from the properties of the
elements that make them.
• Calcium is a soft, silvery,
metallic solid.
• Chlorine is a greenishyellow gas that is
extremely reactive and
poisonous to humans.
• Together they make
Calcium Chloride which is
a non-porous, white solid
used to melt ice on streets
Atoms Combine in Predictable
Numbers
A given compound always contains
atoms of elements in a specific ratio.
Definition of Chemical Formula:
• An expression
that shows the
number and type
of atoms joined
in a compound.
Definition of Subscript
• A number written to
the right of a chemical
symbol and slightly
below it in a chemical
formula.
• The subscript of 1 is
never used.
• Ex) CO2
Use the Chemical Formula chart
on Page 172:
• How many more hydrogen atoms does
propane have than methane?
• Why is the ratio of atoms in a chemical
formula so important?
Use the Chemical Formula chart
on Page 172:
• How many more hydrogen atoms does
propane have than methane? 4
• Why is the ratio of atoms in a chemical
formula so important? Different ratios
of elements indicate different
compounds
The properties of compounds can
be different even if they are made
up of the same elements
6.1 Review Questions, pg. 173
Answer each question in complete
sentences.
Answers to 6.1 Review
1. In many cases, they are different
2. There are 45 total atoms in the formula; 12
carbon, 22 hydrogen, and 11 oxygen.
3. Atoms can combine in many different ratios.
4. All atoms are in a 1:1 ratio.
5. Compare how they react with other substances.
6. The ratios of the compounds are different.
Ch. 6.2
Chemical bonds hold compounds
together
Chemical bonds between atoms
involve electrons
• When do chemical
bonds form?
– When valence
electrons (electrons in
the outermost shell) in
the electron cloud
around two atoms
interact
1. Chemical bonds between
atoms involve electrons
• Atoms can transfer electrons (ionic bonds)
• Atoms can share electrons (covalent bonds)
• Chemical bonds give all materials their
structure.
2. Atoms can transfer electrons.
• When is a positive ion
formed? A positive
ion is formed when an
atom loses electrons.
• When is a negative ion
formed? A negative
ion is formed when an
atom gains electrons
An element’s location on the periodic
table can give a clue as to the type of
ions that atoms of that element will form
• What type of ions do metals
form? + ions (Group 1 loses 1
e-(electron),Group 2 loses 2 e-)
• What type of ions do
nonmetals form?
- ions (Gr. 16 gains 2 e-, Gr. 17
gains 1 e-)
• What group on the table does
not normally form ions? Why?
Noble Gases (group 18); because
their outer energy level are
full.
Ionic Bonds
• How are ionic bonds held
together? by the force of
attraction between positive
and negative ions (transfer
electrons)
• Ionic compounds form
between all nearby ions of
opposite chare. These
interactions make ionic
compounds very stable
and their crystals very
strong.
• Octet Rule – Rule of 8 
8e- in outer shell = stable
atom
Ionic Bonds
• Ionic bonds form
between a metal (+
ion) and a nonmetal(ion).
Ionic Bonds
•
Steps for naming a
chemical compound:
1. Take the name of the
positive metal
element
2. Take the name of the
negative nonmetal
element
3. Combine the two
names.
3. Atoms can share electrons.
Nonmetal atoms usually form bonds
by sharing electrons.
Covalent Bonds
• How are covalent
bonds held together?
By sharing electron
pairs
• How can you help
yourself remember
how covalent bonds
are held together? Co
= partner
What does each line in the model
stand for?
• A shared pair of
electrons
What is a molecule?
• A molecule is a group
of atoms held together
by covalent bonds.
4. Chemical bonds give all
materials their structures.
• What is responsible
for many of the
properties of the
substances? The
structure of their
crystals and molecules
that make it up
Ionic Compounds
• Have a regular crystal
structure
• Because of these rigid
structures, when
enough force is
applied to the crystal it
shatters rather than
bends.
Covalent Compounds
• How are covalent
compounds different from
ionic compounds?
Covalent bonds exist as
individual molecules
• How does molecular
structure affect the
properties of compounds?
Ex. We detect scents
because molecules fit into
receptors in our nose
drugs can work because
molecules fit into specific
receptors in the body.
Polar Covalent Bond
• The unequal sharing
of electrons between
two atoms that gives
rise to negative and
positive regions of
electric charge.
Ch. 6.2 Review Questions pg.182
1. What part of an atom is involved
in bonding?
2. How are ionic bonds and covalent
bonds different?
3. What kind of bond would you
expect strontium and iodine to
form? Why? Name the
compound
Ch. 6.2 Review Questions pg.182
1.
What part of an atom is involved in bonding?
Electrons in the cloud (valence e-)
2. How are ionic bonds and covalent bonds
different? Ionic bonds transfer and are held
together by electrical attraction, covalent
bonds share electrons
3. What kind of bond would you expect
strontium and iodine to form? Why? Name
the compound
Ionic bond – metal + nonmetal
Strontium is in Gr. 2 and forms a + ion; Iodine is
in Gr. 17 and forms a – ion. They have
opposite charges and attract. Name:
Strontium Iodide