Unit 2: Chemical
bonding and
reactions
Module 6: Ionic
compounds and
metals
Lesson 1:
Ion formation
BP:168
Focus Question
Why do elements form compounds?
New Vocabulary
Chemical bond
Cation
Anion
Review Vocabulary
Octet rule: atoms tend to gain, lose, or share
electrons in order to acquire eight valence
electrons.
Valence Electrons and Chemical Bonds
The coral reef is formed
from a compound called
calcium carbonate,
which is just one of the
thousands of
compounds found on
earth. How do so many
compounds form from
the relatively few
elements known to
exist?
The answer involves the
electron structure of
atoms and the nature of
the forces between
atoms
Valence Electrons and Chemical Bonds
You know that elements within a group
on the periodic table have similar
properties. Many of these properties
depend on the number of valence
electrons the atom has.
These valence electrons are involved in
the formation of chemical bonds between
2 atoms.
A chemical bond is the force that holds 2
atoms together.
This chapter discusses chemical
bond formed by ions, atoms that have
acquired a positive or negative charge
https://www.youtube.com/watch?v=x1gdfkvkPTk
Valence Electrons and Chemical Bonds
• Lewis developed electron dot diagrams as a
simple way to show and keep track of valence
electrons
• Electron-dot structures can be used to
illustrate the formation of chemical bonds.
Engage: Valence electrons and chemical bonds
1- Draw the arrangement of electrons in energy levels around nucleus. Identify the number of
valence electrons and electron dot diagram of each of the following elements: Calcium,
Chlorine and Argon.
Element
Arrangement of
electrons in energy
levels around
nucleus
Valence electrons
Calcium
Chlorine
Argon
2- What must calcium do to acquire 8 valence electrons ?
3- What must chlorine do to acquire 8 valence electrons?
Electron Dot
Diagram
Valence Electrons and Chemical Bonds
• Elements tend to react to acquire the stable
electron structure of a noble gas.
• Atoms try to form an octet—a stable
arrangement of eight valence electrons in the
outer energy level—by gaining or losing
valence electrons.
Watch the following video, and describe how the bond in NaCl is formed and why ?
https://www.youtube.com/watch?v=lhC42qxk5kQ&t=48s
Explore and explain: Positive Ion Formation
Alkali metals (Group 1) tend
to lose one electron to form
1+ ions. Sodium forms many
common compounds including
salt and baking soda
The alkaline earth metals (Group 2) tend to
lose 2 electrons and form 2+ ions. Elemental
beryllium is a hard brittle metal. In nature,
beryllium is found combined with other elements
to form a variety of minerals, such as beryl
Explore and explain: Positive Ion Formation
Some Transition metals form several
different ions. For example copper,
shown here as a native mineral,
commonly 1+ and 2+ ions in
compounds.
Positive Ion Formation
Metals, which are located
on the left side of periodic
table, easily lose electrons
A positive ion forms
when an atom loses one or
more valence electrons in
order to attain a noble gas
configuration.
A positively charged ion
is called a cation.
Positive Ion Formation
•
•
This figure illustrates how
sodium loses a valence electron
to become a sodium cation.
By losing an electron, the
sodium atom acquires the
stable outer electron
configuration of neon.
Analyze: Does the removal of an
electron from a neutral atom
require energy or release energy?
Positive Ion Formation
• Metals atoms are reactive because they lose
valence electrons easily. Group 1 and 2 metals are
the most reactive metals.
• The ions formed by metal atoms in groups 1, 2, and
13 are summarized below.
Group
Charge of ion formed
1 (lose 1 electron)
1+
2 (lose 2 electrons)
2+
13 (lose 3 electrons)
3+
Positive Ion Formation
Most transition metals ,group 14 metals and
some of group 13 metals form ions with charge
of +2, +3 or more
The following table shows the most common
one.
Positive Ion Formation
Use Graphic organizers
In your chemistry journal, make a chart with the following
column heads: Symbol of element, electron dot diagram,
Ion with charge, number of electrons Lost or gained, and
name of ion.
Complete the table using the elements Cesium, barium,
Zinc, Phosphorus, copper, Iron, Chromium
Negative Ion Formation
While metals tend to form positive ions, nonmetals tend to form negative
ions. For nonmetals, you can usually predict the charge of the negative
ion that an element will form simply by looking at the element’s group on
the periodic table.
Explore and explain: Negative ion formation
Carbon, seen here in one of its
elemental forms, is in group 14.
From this, you might predict that it
will form a 4- ion. While this is
possible, the ion is very unstable
and uncommon.
Explore and explain: Negative ion formation
Elemental phosphorus has 2
major forms- white and red. When
phosphorus ionizes, it tends to
form 3- ions. Notice
phosphorus’s position in group
15
Explore and explain: Negative ion formation
Oxygen from group 16, tends to form
2- ions.
Explore and explain: Negative ion formation
Bromine, a brown liquid in its
elemental form, is in group 17.
Group 17 elements tend to be
very reactive, easily forming 1ions.
https://wordwall.net/resource/255
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76668
Negative Ion Formation
• The figure shows
chlorine gaining an
electron. This process
releases 449 KJ/mol
• An anion is a negatively
charged ion. Thus, the
chlorine atom becomes
a chloride anion.
Compare
How do the energy changes accompanying
positive ion and negative ion formation
compare?
Negative Ion Formation
• As shown in the table, nonmetal ions gain
the number of electrons required to fill an
octet valence shell
Group
Charge of ion formed
15
3-
16
2-
17
1-
Naming monatomic ions (one atom ion)
Cations of Group 1, and 2 metals: Name of the metal + “ion”
Example: Na+ is sodium ion
Transition metals cations:
“ion ”
Metal name + Roman numerals +
Example: Fe3+ is iron (III) ion
Anion names: Nonmetal root name + “-ide ” + ion
Example: Cl- is chloride ion
Elaborate
https://quizizz.com/admin/quiz/6242f4d745
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Answer the focus question of this lesson:
Why do elements form compounds?
Evaluate
1- Determine the ions formed from
strontium (Sr), aluminum (Al) and sulfur (S)
2- What ion will form when fluorine (F)
reacts? What is the name of this ion?
Explain
Check your progress
Check your progress
Quiz
1. What is true of a chemical bond?
A
It is the force that holds two atoms together.
B
It is never formed by ions.
C
It is formed only by ions.
D
It forms by the attraction between the
positive nucleus of one atom and the
positive nucleus of another atom.
CORRECT
Quiz
2. Which best describes why atoms try to form an
arrangement of eight valence electrons in their outer
energy level?
A to gain electrons
B
to lose electrons
C
to form ions
D
to acquire the stable electron structure of a CORRECT
noble gas
Quiz
3. Which of the following is true?
A
Anions are positively charged ions.
B
A chloride ion is a cation.
C
A sodium ion is an anion.
D
Cations are positively charge ions.
CORRECT
Quiz
4. Which metals are the most reactive?
A
metals in groups 1 and 3
B
metals in groups 1 and 2
C
metals in groups 2 and 13
D
Metals are not reactive.
CORRECT
Quiz
5. Which letter on the graph represents the zone of
physiological stress?
A
They are not reactive.
B
They all have noble gas configurations.
C
They are found on the left side of the periodic
table.
They easily gain electrons to attain a
CORRECT
stable outer electron configuration.
D
lesson 2:
Ionic Bonds
and Ionic Compounds
BP:173
Focus Question
How are the ions in ionic compounds
arranged?
New Vocabulary
ionic bond
ionic compound
crystal lattice
Electrolyte
lattice energy
Review Vocabulary
compound: a chemical combination of two or
more different elements
Engage: Formation of an Ionic Bond
Formation of an Ionic Bond
- The electrostatic force that holds oppositely charged
particles together in an ionic compound is referred to
as an ionic bond.
- Compounds that contain ionic bonds are ionic
compounds
Formation of an Ionic Bond
- If ionic bonds occur
between metals and
the non metal oxygen,
oxides form.
- Most other ionic
compounds are called
salts
Explore and explain: Formation of an Ionic
Bond
-Sodium and chlorine react vigorously, forming the
common ionic compound table salt.
-During this reaction, a sodium atom transfers its
valence electron to a chlorine atom and becomes a
positive ion. The chlorine atom accepts the electron
into its outer energy level and becomes negative ion
- The oppositely charged ions attract each other,
forming the compound sodium chloride
Explore and explain: Formation of an Ionic Bond
Magnesium and oxygen
react to produce the ionic
compound magnesium
oxide, which has uses in
environmental
remediation
Explore and explain: Formation of an Ionic Bond
Aluminum and bromine
also release a good deal
of energy when they
react, producing the ionic
compound aluminum
bromide
Formation of an Ionic Bond: Binary ionic compounds
• Binary means that the compounds contain
only two different elements.
• Binary ionic compounds contain a metallic
cation and a nonmetallic anion.
• Sodium chloride (NaCl) is a binary compound.
Formation of an Ionic Bond: Binary ionic compounds
What role does ionic charge play in the
formation of ionic compounds?
Formation of an Ionic Bond: Binary ionic compounds
-
What role does ionic charge play in the formation of ionic
compounds?
Ionic compounds are electrically neutral and the number
of electrons lost and gained must be equal
consider how calcium Fluoride forms:
Calcium needs to lose two electrons and Fluorine
must gain 1 electron. The number of electrons lost
and gained must be equal SO two fluorine atoms are
needed to accept the two electrons lost from calcium
atom
Formation of an Ionic Bond: Binary ionic compounds
Properties of Ionic Compounds
Electrical forces in ionic bonds
produce unique physical
structures.
- Physical structures:
The ions are packed into a
repeating pattern that balances
the forces of attraction and
repulsion between the ions.
Properties of Ionic Compounds
• The strong attractions among the positive ions and
the negative ions in an ionic compound result in
the formation of a crystal lattice.
• A crystal lattice is a three-dimensional geometric
arrangement of particles.
Properties of Ionic Compounds
Physical properties
• Melting point, boiling point, and hardness are
physical properties. They are determined by
the strength of electrical forces between
particles in matter.
• Ionic bonds are relatively strong, so ionic
crystals require a lot of energy to be broken
apart. Thus, the crystals have high melting
and boiling points.
Properties of Ionic Compounds
Properties of Ionic Compounds
•
•
Ionic crystals are hard, rigid, brittle solids due to the
strong attraction between electric charges that hold
the ions in place.
This figure shows how and why crystals break when a
force strong enough to overcome these attractive
forces is applied.
Properties of Ionic Compounds
• The ability of a material to conduct electricity depends
on the availability of freely moving charged particles, so
whether they are free to move determines whether an
ionic compound conducts electricity.
• In a solid, ions are locked in position by strong
attractive forces. Thus, ionic solids are poor conductors.
• In ionic compounds in solution or a liquid state, ions
are free to move. Thus, these compounds conduct
electricity.
• An ionic compound whose aqueous solution conducts
an electric current is called an electrolyte.
Energy and the Ionic Bond
• During a chemical reaction,
energy is either absorbed or
released.
• Reactions that absorb energy are
endothermic.
• Reactions that release energy are
exothermic.
Energy and the Ionic Bond
• The formation of ionic compounds from positive
ions and negative ions is always exothermic.
• The attraction of the ions forms a more stable system
that is lower in energy than the individual ions.
Energy and the Ionic Bond
• Because ions in ionic compound are arranged
in crystal lattice, the energy required to
separate 1 mol of ions of an ionic compound
is the lattice energy.
• The strength of the electrical forces holding
ions in place is reflected by the lattice energy.
• The greater the lattice energy, the stronger
the force of attraction.
Energy and the Ionic Bond
•
•
•
Lattice energy is related to ion size.
The electrostatic force of attraction between
opposite charges increases as the distance
between the charges decreases.
Smaller ions form compounds with more closely
spaced ionic charges, so they have stronger
attractions and greater lattice energies.
Explain:Energy and the Ionic Bond
Explain the relationship between lattice energy
and the size of ions in an ionic compound
Energy and the Ionic Bond
- The value of lattice energy is also affected by the
charge of the ion.
- The ionic bond formed from the attraction of ions
with larger positive or negative charges
generally has a greater lattice energy
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001d74c865?source=quiz_share
Energy and the Ionic Bond
1- Notice the lattice
energy of SrCl2 and
AgCl. How do they
show the relationship
between lattice energy
and charge of ions
involved?
Elaborate
Answer the focus question of this lesson:
How are the ions in ionic compounds arranged?
Evaluate
1- Determine the ionic compound formed from Mg
and Cl. Explain the formation
2- Using aluminum and oxygen, determine the
formula of ionic compound formed .
Quiz
1. Which of the following is not an ionic compound?
A
magnesium oxide
B
sodium chloride
C
water
D
barium sulfate
CORRECT
Quiz
2. Identify the binary ionic compound.
A
H2O
C
NaCl
B
C6H12O6
D
Be3Al2Si6O18
CORRECT
Quiz
3. What term best describes the structure formed by the
strong attractions among the positive ions and the
negative ions in an ionic compound?
A a mineral
B
an oxide
C
a salt crystal
D
a crystal lattice CORRECT
Quiz
4. Which of the following is true of ionic crystals?
C
Ionic bonds are strong, so ionic crystals require a
large amount of energy to be broken. CORRECT
Ionic crystals have low melting points and high
boiling points.
Ionic crystals are malleable, not brittle.
D
Ionic crystals always conduct electricity.
A
B
Quiz
5. Which of the following is correct?
A
B
C
D
Lattice energy is the energy needed for 1 mol of
positive ions to bond with 1 mol of negative ions.
Ions in an ionic compound are arranged in a
random pattern.
Ionic compounds are never electrolytes.
Ionic compound properties are related to ionic
bonding. CORRECT