April 30
Day 6
DRQ: What is an ion?
Activities:
 DRQ/Review DRQ
 Review Test
 Chapter 11 Introduction
Homework: Complete Why Atoms Combine
Cornell Notes pages 298 -302
Chapter 11
Chemical Bonds
Pages 296-321
Introduction to
Chemical Bonds pg 297
• Chemical Bonds
• The explosion of fireworks are chemical
changes in which chemical bonds are
broken
• When a chemical bond is broken, energy is
usually released
• The explosion happens when substances
in fireworks combine (bond) with oxygen
in the atmosphere
• These combinations happen because the
electrons in atoms can be given away or
borrowed.
• Remember, chemistry is all about electrons,
the nucleus of an atom will rarely change – that
is called radioactivity.
Fireworks!
• Today's fireworks rely on black powder for two
critical functions.
• Gas released when the powder combusts first propels
the firework skyward (Newton’s third law of motion)
• Later the black powder inside blasts its contents
outward into the patterns that spectators come to
see.
• However, other chemical ingredients are also
needed; without them fireworks would produce
little more than yellowish-orange sparks and
white smoke.
• Here is how they make those great colors…
Chapter 11 Chemical Bonds
Section 1: Why Atoms Combine
Pages 298-302

Words to know:
–
–
–

Chemical Formula
Chemically Stable
Chemical Bond
Objectives/Study Questions
1. Describe how a compound differs from the
elements that compose it.
2. Explain what a chemical formula represents.
3. State a reason why chemical bonding occurs.
11.1 Summary
1.
Compounds have different properties than their elements.
When a bond forms, the properties change.
1.
2.
2.
A chemical formula tells you what elements make up the
compound and in what ratio.
1.
2.
3.
Remember Na (highly reactive metal) and Cl (poisonous green gas)
combine to NaCl (edible crystalline solid, dissolves in H2O)
H is a light flammable gas, O is also a flammable gas, add two H to an
O and you get a clear, colorless liquid.
H2O has two atoms of H for every one atom of O
NaCl has one atom of Na for every one atom of Cl
A Chemical bond is how atoms share, lose or gain
electrons that will help them become more stable. It joins
two atoms together.
1.
Na is highly reactive, so is Cl, when they bond with each other, they
are less reactive.
Some bonding
background info…

Atoms with a full outer energy level are
chemically stable – they will not react
with another atom to form a new
substance


Which elements are these?
For most atoms, this means it has 8 outer
electrons.
– This is called the octet rule

For H and He what should this rule be called?
More bonding
background…

Most metals have 3 or fewer outer electrons
and tend to lose electrons to form positive
ions.
– These will react with negative ions to form new
compounds

Most non metals have 5 or more outer
electrons and tend to gain electrons to form
negative ions.
– These will react with positive ions to form new
compounds.
Cornell Notes
pages 298-302

Take notes on:
– Compounds
– Formulas

See examples of these on page 300
– Chemically stable atoms

Make sure you draw some examples of Dot
diagrams
May 1
Day 1
DRQ: Why do atoms combine?
Activities:
 DRQ/Review DRQ (check homework
completion)
 Review Notes for 11.1
 Section Wrap up page 302
Homework: Complete Section Wrap up
Compounds
Most matter is a compound or a mixture of
compounds

–

A compound has different physical properties than the
elements that combined to form the compound.
The physical properties of the elements are gone,
they are replaced by the physical properties of the
new compound.
1.
2.
Na (highly reactive metal) and Cl (poisonous green
gas) combine to NaCl (edible crystalline solid that
dissolves in H2O)
H is a light flammable gas, O is also a flammable gas,
add two H to an O and you get a clear, colorless
liquid.
Check out this clip…
Formulas

Formulas are made up of chemical symbols.
– This is a shorthand way of naming the atoms in a
compound


What is the formula for Water?
What does the formula mean?
– A subscript is a number “written below” and after
the chemical symbol.
– The subscript tells how many atoms of that element
are in the compound

Fe2O3 has two Iron atoms chemically combined with three
Oxygen atoms
Chemical Formula

The chemical formula for any
compound tells
1. What elements it contains
2. The ratio of the atoms of those elements.

Look at table 11-1 on page 300.
– What elements are in each compound?
What is the ratio of atoms in each
compound?
Chemically Stable Atoms

Most elements form compounds because it
makes them chemically stable.
– An atom is chemically stable if its outer energy
level is filled with electrons
– A dot diagram is used to quickly show how many
outer level electrons an atom has.

In this video you’ll see how two Cl atoms
SHARE two valence electrons.
– It also shows the use of dot diagrams to indicate
the electrons in the outer energy level and how
they are shared in a bond.
– This type of bond is called covalent.
Chemical Bonds



A chemical bond is a force that holds the atoms in a
substance together.
You just saw how two Cl atoms can share electrons to
create a bond.
Here is how a chemical bond forms between Mg and O
– When Mg and O become bonded, each Mg loses two electrons
and each O gains two electrons.
– The bond forms because Mg has 2 extra + charges and the O
has 2 extra – charges and they are attracted to each other.

This video segment should help you visualize this
process.
Valence Electrons

As you saw in the videos, for most
elements the outer energy level
(valence) is most stable when it
contains eight electrons.
– Why would Krypton be considered
chemically stable?
– Why is H so unstable?
Outer Levels:
Giving, Stealing and Sharing

Atoms that do not have eight outer level
electrons will bond with atoms of other
elements to fill an octet (eight electrons)
– They do this by gaining, losing or sharing
electrons
What happens to an atom if it loses an electron?
 What happens to an atom if it gains an electron?
 When atoms SHARE electrons they have to be
close enough that their electron clouds
intermingle.

Complete the Section Wrap-up Page 302
Questions 1-4 and the Skill Builder
ANSWER 1 and 3 IN FULL SENTENCES!
1.
2.
What happens to the properties of elements when
atoms form compounds? The property of elements…
Write formulas for
a.
b.
3.
4.
A compound with one calcium atom and two fluorine atoms
A compound with two aluminum atoms and three sulfur
atoms
Why do most elements tend to form compounds?
Most elements tend to form compounds to/because
The label on a box of washing soda states that it
contains Na2CO3.
a.
b.
Name the elements in the compound.
In what ratio are the elements present?
Skill Builder

Look at Table 11-1 on page 300.
There are two kinds of chemicals in this table,
organic and inorganic.
Chemicals with Carbon in them are considered
organic.
Carbon is an amazing element.
It can form one, two, three and even four bonds.
Check out this video. See if notice anything about
the bonds they show…
Re-create this table


Organize it by the type of compound,
Organic or Inorganic.
Hint (there are three organic
compounds and six inorganic
compounds)
Not Done?


Finish these questions for homework.
You will find them on page 302 of your
textbook.