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Ionic and
Metallic Bonding
Chapter 7
Introduction
• Ions are atoms that have either a positive
or negative charge.
• Ions form to obtain a more stable
configuration.
• Ionic compounds form when ions of the
opposite charges interact.
• We can represent ions and ionic
compounds using chemical symbols and
formulas.
• Metal atoms also bond.
Ions
Section 7.1
• Valence Electrons
• The Octet Rule
• Formation of
Cations
• Formation of
Anions
I.) Valence Electrons
The electrons in the highest
occupied energy level of an
element’s atoms.
• Valence electrons account for almost all the
chemical behavior of an element and all
chemical bonds.
• Elements within each group behave similarly
because they have the same number of
valence electrons.
• The number of valence electrons is related to
the group numbers in the periodic table (the
American and European numbering system)
How many valence electrons are in
each atom?
1. potassium
2. carbon
3. magnesium
4. oxygen
Lewis Dot Structure
Lewis dot structures (or electron dot
structures) are diagrams that show
valence electrons as dots.
Draw the Lewis Dot Structure for
the Following Atoms.
1. potassium
2. carbon
3. magnesium
4. oxygen
The Octet Rule
In forming compounds, atoms tend to
achieve the electron configuration of a
noble gas.
Recall: All noble gases have eight electrons
in their highest occupied energy levels.
ns2np6
Cations
• These are positively charged ions,
resulting from a loss of an electron.
• Metals tends to lose electrons from their
highest occupied energy levels to become
cations. This leaves a complete octet in
the next-lowest energy level.
• The charge for a cation is written as a
number followed by a plus sign.
– Na1+
– Ca2+
Representing the Formation of Cations
• Atoms tend to lose their valence electrons to
become cations.
– Na → Na+ + e– Ca → Ca2+ + 2e-
• The name of the metal is the same as the name
of the ion.
• Most metal atoms have between 1 and 3
valence electrons they can lose.
• Since the number of protons do not change, a
loss of an electron gives the cation a net positive
charge.
Na
1s22s22p63s1
How many
e- lost?
Na+
1s22s22p6
What noble gas
does this
resemble?
We can represent the above reaction using
Lewis dot structures.
Cations of Transition Metals
• The charges of cations of a transition
metal may vary. They may lose different
numbers of electrons.
– Some transition metals may have multiple
charges.
• Some ions formed by transition metals do
not have noble-gas electron configuration.
– These ions are exception to the octet rule.
– These have pseudo noble-gas configuration.
Examples of Cations of Transition
Elements
Iron
[Ar]4s23d6
Fe2+
[Ar]4s13d5
Silver
[Kr]5s14d10
Ag+
[Kr]4d10
•
•
Fe3+
[Ar]3d5
All orbitals are filled and thus becomes
relatively stable. This is the pseudo noble gas
configuration.
Au, Cd, and Hg also have pseudo noble gas
configurations.
Anions
• These are negatively charged ions
resulting from a gain of electrons.
• Nonmetals tend to add or share
electrons into their highest occupied
energy levels to become anions. This
allows them to achieve an octet in their
highest occupied energy level.
• The charge for an anion is written with a
number followed by a negative sign.
– Cl1– F1-
Representing the Formation of
Anions
• Atoms tend to accept electrons into their
highest occupied energy levels to become
anions.
– e- + Cl → Cl– e- + F → F-
• Name of the anion of a nonmetal ends in
-ide. (chlorine = chloride ion).
• Since the number of protons do not
change, a gain of an electron gives the
anion a net negative charge.
Cl
1s22s22p63s23p5
How many
e- gained?
Cl1s22s22p63s23p6
What noble gas
does this
resemble?
We can represent the above reaction using
Lewis dot structures.
Some Common Anions
1-
2-
F- fluoride
Cl- chloride
O2S2-
Br- bromide
SO42- sulfate
I-
CO32- carbonate
iodide
OH- hydroxide
ClOhypochlorite
NO3- nitrate
oxide
sulfide
3N3- nitride
PO43- phosphate
Ionic Bonds and
Ionic Compounds
Section 7.2
• Formation of
Ionic
Compounds
• Properties of
Ionic
Compounds
Barite
BaSO4
Aragonite
CaCO3
Introduction to Ionic Compounds
• Ionic compounds are formed from the
interaction between an anion and a cation.
• Ionic compounds are usually composed of a
metal cation and a nonmetal anion.
• Ionic compounds are electrically neutral: the
total positive charge is equal to the total negative
charge.
• Ionic compounds are held together by the
attraction of the cations to the anions, this
attraction is known as an ionic bond.
I.) Formation of the Ionic Bond
Ionic bonds: The electrostatic forces that
hold ions together in ionic compounds.
Let’s see how this bond forms for NaCl.
Na
Cl
1s22s22p63s1 1s22s22p63s23p5
Na+
Cl1s22s22p6
1s22s22p63s23p6
Write the Lewis Dot Structure for
the Previous Reaction.
Na
+
Cl
(1s22s22p63s1)
(1s22s22p63s23p5 )
Na+
+
Cl(1s22s22p6) (1s22s22p63s23p6 )
How Would Potassium React with
Bromine?
K
+
Br
KBr
Representing Ionic Compounds
• Ions in a solid ionic compound are
arranged in an orderly pattern. They do
not exists as discrete units even though
we write them so.
• We can represent the composition of a
substance using chemical formulas.
• A formula unit is the lowest wholenumber ratio of ions in an ionic compound.
Ions Do Not Exists as Discrete
Units in an Ionic Compound
Na+ Cl-
Though we can write ions as individual units.
Chemical Formulas
A chemical formula shows the kinds and
numbers of atoms in the smallest
representative unit of a substance.
For example:
1.) NaCl : sodium chloride
2.) BaF : barium fluoride
Formula Unit
The lowest whole-number ratio of
ions in an ionic compound.
• We use formula units because ionic compounds
exists as a collection of positively and negatively
charged ions arranged in repeating patterns.
• To determine formula units we need to keep in
mind that ionic compounds must remain neutral.
Determining Formula Units
• Make sure that the charge is zero once
formula units have been assigned.
• Example:
– Na+ + Cl-
Na1Cl1
• Let’s do this for the ionic compound
formed between lithium and chlorine.
1. Determine the formula units for the
compound formed between magnesium
cations and chloride anions.
2. Determine the formula units for the
compound formed between lithium
cations and chloride anions.
Short Cut to Writing Chemical
Formulas
1. Determine the charge of the cation and
the anion
2. Use these charges as the subscripts for
the opposing ion.
3. It’s that easy.
Let’s try this for sodium oxide
Write the formulas for each compound:
1. barium chloride
2. magnesium oxide
3. lithium oxide
4. calcium fluoride
Properties of Ionic Compounds
• Most are crystalline solids at room
temperature.
• Ionic compounds generally have very high
melting points.
• Ionic compounds can conduct an electric
current when melted or dissolved in water.
Ionic Compounds Are Solids
• Many are crystalline solids
• Components in these crystals are
arranged in repeating 3-D patterns.
• In this arrangement, each ion is attracted
strongly to each of its neighbors and
repulsions are minimized.
Ionic Compounds Have High
Melting Points
• There are large attractive forces between
the ions.
• Their arrangement around each other
maximizes these attractive forces and
minimizes the repulsive ones.
• Therefore, a great deal of energy is
required to break the bonds between ions
in an ionic compound.
Ionic Compounds Conduct
Electricity
• Ionic solutions and molten ionic
compounds conduct electricity.
• Ions are charged and so they can conduct
electricity very well.
• When a voltage is applied the cation
migrates to the negative electrode and the
anion towards the positive one, thus
creating a current.
What are Metals?
Metals are
made up of
closely
packed
cations rather
than neutral
atoms.
The Metallic Bond
“Sea-ofElectrons”
Model
Metallic bonds consist of
the attraction of the freefloating valence electrons
for the positively charged
metal ions.
“Sea-of-Electrons” Explains
Metallic Properties
Alloys
Mixtures composed of two or more
elements, at least one of which is a metal.
Bronze
Sterling Silver
• Alloys have properties that are often
superior to those of their component
elements.
– Sterling Silver: (92.5% Ag & 7.5% Cu) Harder
and more durable than pure silver.
– Bronze: (~70% Cu & 10% Sn) Harder than
copper and more easily cast.
• Alloys can form in different ways.
– Substitutional alloy: Component atoms
about the same size.
– Interstitial alloy: Component atoms are quite
different in size.
Ionic and
Metallic Bonding
Chapter 7
The End