The Structure of Matter
Chapter 6
Section 1: Compounds and Molecules
Bellringer
Study the models of the water molecule, H2O, and the carbon
dioxide molecule, CO2, and then answer the items that follow.
1. Name some similarities between the molecules of H2O
and CO2.
2. How are the molecules different?
Open Your Books To Page
177
Chemical Bonds
〉What
holds a compound together?
〉The
forces that hold atoms or ions together in a
compound are called chemical bonds.

chemical bond: the attractive force that holds atoms or
ions together
Atoms and ions are held together
by
1.
2.
3.
4.
Nuclear bonds
Stick bonds
Physical bonds
Chemical bonds
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4
Which of the following is a
compound?
1.
2.
3.
4.
Salt
Paint
Soup
Air
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2
3
4
Visual Concept: Compounds
Visual Concept: Chemical Bond
Chemical Structure
〉How
can the structure of chemical compounds be
shown?
〉The
structure of chemical compounds can be shown
by various models. Different models show different
aspects of compounds.

chemical structure: the arrangement of atoms in a substance
Chemical Structure, continued

Some models represent bond lengths and angles.
• bond length: the average distance between the nuclei of two
bonded atoms
• bond angle: the angle formed by two bonds
to the same atom
Visual Concept: Bond Angle
Chemical Structure, continued

In a ball-and-stick model, atoms are
represented by balls. The bonds that
hold the atoms together are
represented by sticks.

In structural formulas, chemical
symbols are used to represent the
atoms.

Space-filling models show the
space occupied by atoms, but not
bond lengths.
Which of the following models could be used to
compare the sizes of atoms in a molecule?
1.
Ball-and-stick
2.
Structural
3.
Space-filling
4.
Formula
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A compound with only two atoms
would not have a
1.
2.
3.
4.
Chemical structure
Chemical bond
Bond length
Bond angle
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1
0
0
2
3
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4
Which of the following would show
bond angle?
1.
2.
3.
4.
Ball-and-stick
Structural
Space-filling
formula
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2
3
4
BELLRINGER #2

Name and Describe the three kinds of
ways we can show chemical structure.
Chemical Structure, continued

In a ball-and-stick model, atoms are
represented by balls. The bonds that
hold the atoms together are
represented by sticks.

In structural formulas, chemical
symbols are used to represent the
atoms.

Space-filling models show the
space occupied by atoms, but not
bond lengths.
Chemical Structure, continued

Bonds can bend, stretch, and rotate without breaking.
◦ Bonds can be represented by flexible springs.
◦ Most reported bond lengths are average distances.
◦ Bonds hold atoms together tightly.
How Does Structure Affect Properties?
〉What
〉The
determines the properties of a compound?
chemical structure of a compound determines
the properties of that compound.
How Does Structure Affect Properties?
continued
 Compounds with network structures are
strong solids.
◦ Example: Quartz, SiO2 is made of silicon
and oxygen atoms.
◦ The atoms are bonded in a strong, rigid structure.
There are strong bonds between the atoms in a
piece of quartz. These bonds give quartz a
0
1.
0
2.
0
3.
0
4.
Low melting point
High melting point
Low molecular mass
High molecular mass
30
How Does Structure Affect Properties? continued

Some networks are made of bonded ions.
◦ The strong attractions between the
oppositely charged ions give ionic
compounds high melting points and
high boiling points.
◦ Example: Table salt—sodium chloride—
is made
of a tightly packed repeating network
of positive sodium ions and negative
chlorine ions.
How Does Structure Affect Properties? continued
 Some compounds are made of molecules.
◦ Some compounds made of molecules are solids, others
are liquids, others are gases.
◦ The strength of attractions between molecules varies.
◦ Attractions between water molecules are called hydrogen
bonds.
 Hydrogen bonds are not as strong as the bonds holding oxygen
and hydrogen atoms together within a molecule.
The attraction between molecules tends to
be ____ the attraction between ions.
1.
2.
3.
4.
Weaker than
Stronger than
Equal to
None of the above
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3
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4
Which molecules are most strongly
attracted to one another?
Water molecules
2. Hydrogen molecules
3. Oxygen molecules
4. Nitrogen molecules
1.
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2
3
4
Sugar has a lower melting point than salt
because sugar is made of
1. Atoms
0
2.
Ions
3.
Molecules
4.
Crystals
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A hydrogen bond BETWEEN water molecules is
which of the following when compared to the
bonds within an individual water molecule?
It is stronger
2. It is weaker
3. It is the same strength
4. None of the above
1.
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1
2
3
4
Participant Scores
25
Sharlie Ward
15
Andrew Dickason
20
20
20
20
Alexis Ramsey
Shania Warren
Gianna Davila
Callie Huffman
15
10
10
10
Ahlam Esmail
Kristian Coons
Megan Gatta
Carly Palumbo
20
15
15
Linzy Thomas
Jacquelyn Staley
Pat Sturgeon
10
10
10
Isaiah Hudson
Zack Click
Amber Orr
15
15
Dezirae Davies
Abby Sattler
5
Kaitlin Soucy
For Homework:
Section Review
p. 182 (1-6)