Transcript IONIC COMPOUNDS

IONIC COMPOUNDS
Chapter 8
Forming Chemical Bonds
Section 8.1
 The force that holds two atoms
together is called a chemical
bond.
 Chemical bonds may form by the
attraction between a positive
nucleus and negative electrons or
the attraction between a positive
ion and a negative ion
Review…
 Valence electrons are the electrons in the
outermost energy level. These same
electrons are involved in the formation of
chemical bonds between two atoms
Electron-Dot Structures
Especially useful when illustrating
formation of chemical bonds!!
From Chapter 6…
 Ionization energy refers to how easily
an atom loses an electron.
 Noble gases, having high ionization
energies, show a general lack of
chemical reactivity
 The difference in reactivity is directly
related to the valence electrons
Elements tend to react to acquire the
stable electron structure of a noble
gas (V.E. 8)
Formation of Positive Ions
 A positive ion forms when an atom
loses one or more valence electrons
in order to attain a noble gas
configuration
Positively
charged ion
is called a
cation
Transition Metals
 When forming positive ions, transition
metals commonly lose their valence
electrons, forming 2+ ions.
 However, it is also possible for d
electrons to be lost
 A useful rule of thumb for these
metals is that they form ions with a
2+ or 3+ charge.
 Nonmetals have a great attraction for
electrons and from stable outer
electron configuration by gaining
electrons
Negatively
charged ion
is called an
anion
Checkpoint
 Why do ions form?
 Describe the formation of positive and
negative ions.
 Predict the change that must occur to
achieve noble gas stability
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Nitrogen
Sulfur
Barium
Lithium
Answers
 Atoms gain stability by losing or gaining
electrons
 Positive ions form when atoms lose valence
electrons
 Negative ions form when valence electrons are
added to an atom
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Nitrogen- gain 3 electrons (N3-)
Sulfur- gain 2 electrons (S2-)
Barium- lose 2 electrons (Ba2+)
Lithium- lose 1 electron (Li1+)
The Formation and Nature of Ionic
Bonds (Section 8.2)
 The electrostatic force
that holds oppositely
charged particles together
in an ionic compound is
referred to as an ionic
bond
 Ionic bonds form between
cations (+) and anions (-)
 Binary compounds contain
two different elements
 Metallic cation
 Nonmetallic anion
Electrons gained = electrons lost
OVERALL CHARGE OF THE COMPOUND FORMED MUST BE ZERO!!!
Properties of Ionic Compounds
1. High Melting and boiling points
(indicating strong bond
strength)
2. Most are crystalline solids at
room temperature
3. ions in a regular, geometric
pattern (crystal lattice)
4. hard, brittle
5. conduct electricity when
molten or dissolved in water
(aka electrolyte)
Names and Formulas for Ionic Compounds
(Very Important!)
Section 8.3
 Terms to be familiar with:
 Formula Unit- the simplest ratio of the
ions represented in an ionic compound
 Monatomic Ion- a one-atom ion (Mg2+ or
Br1-)
 Oxidation Number- the charge of the
monatomic ion
 Polyatomic Ion- ions made up of more
than one atom (i.e. Nitrite= NO2-)
Write the correct formula for the ionic
compound composed of the following pairs
of ions
1.
2.
3.
4.
Potassium and iodine
Magnesium and chlorine
Aluminum and bromide
Cesium and nitride
Answers
1. Potassium and iodine
K+1 and I-1
 KI
(1:1 ratio)
2. Magnesium and chlorine
Mg+2 and Cl-1  MgCl2 (1:2 ratio)
3. Aluminum and bromide
Al+3 and Br-1  AlBr3 (1:3 ratio)
4. Cesium and nitride
Cs+1 and N-3  Cs3N (3:1 ratio)
Compounds Containing Polyatomic
Ions
 The charge given to a polyatomic ion
applies to the entire group of atoms
 The polyatomic ion acts as an individual ion
 NEVER CHANGE THE SUBSCRIPTS
WITHIN THE ION
 If more than one polyatomic ion is needed,
place parentheses around the ion and write
the appropriate subscript outside the
parentheses.
Practice Problems
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Calcium and Nitrate
Aluminum and Hydroxide
Barium and Sulfate
Sodium and Phosphate
Potassium and Sulfate
Naming Ionic Compounds
 Oxyanion- a polyatomic ion composed
of an element, usually a nonmetal,
bonded to one or more oxygen atoms
 An ion with more oxygen atoms is
named using the root of the nonmetal
plus the suffix –ate (ex. NO3-  nitrate)
 An ion with fewer oxygen atoms is
named using the root of the nonmetal
plus the suffix –ite (ex. NO2-  nitrite )
Chlorine’s 4 Oxyanions
 ClO4-  perchlorate (most oxygen's)
 ClO3-  chlorate (one less oxygen)
 ClO2-  chlorite (two fewer oxygen's)
 ClO-  hypochlorite (three fewer oxygen's)
Naming Ionic Compounds
1. Name the cation (+) first and the
anion (-) second.
2. Monatomic cations use the element
name.
3. Monatomic anions take their element
name plus the suffix –ide.
4. Group 1A and Group 2A metals have only
one oxidation number (charge). Transition
metals and metals on the right side of the
periodic table often have more than one
oxidation number.
 The oxidation number is written as a
Roman numeral in parentheses after the
name of the cation
5. If the compound contains a polyatomic ion,
simply name the ion.
Practice problems
1.
2.
3.
4.
5.
NaBr
CaCl2
KOH
Cu(NO3)2
Ag2CrO4
Cation + Anion
1.
2.
3.
4.
5.
NaBr  sodium bromide
CaCl2  calcium chloride
KOH  potassium hydroxide
Cu(NO3)2  copper (II) nitrate
Ag2CrO4  silver chromate
Section Review
Anion Oxide
Cation 
Potassium
Barium
Aluminum
Ammonium
Chloride
Sulfate
Phosphate
Answers
Anion
Cation 
Oxide
Chloride
Sulfate
Phosphate
Potassium
K2 O
KCl
K2SO4
K3PO4
Barium
BaO
BaCl2
BaSO4
Ba3(PO4)2
Aluminum
Al2O3
AlCl3
Al2(SO4)3
AlPO4
(NH4)2SO4
(NH4)3PO4
Ammonium
(NH4)2O
NH4Cl
Metallic Bonds and Properties of
Metals (Section 8.4)
 Although metals do not bond ionically,
they often form lattices in the solid
state.
 Electron sea model- all the metal
atoms in a metallic solid contribute
their valence electrons to form a
“sea” of electrons
 The electrons present in the outer
energy levels of the bonding metallic
ions are not held by any specific atom
and can move easily from one atom
to the next. (Delocalized electrons)
 A metallic bond is the attraction of a
metallic cation for delocalized
electrons
Metal Alloys
 A mixture of elements that has metallic
properties
 Substitutional- atoms of the original metallic
solid are replaced by other metal atoms of
similar size
 Brass, pewter, 10-carat gold, and sterling silver
 Interstitial- formed when small holes in a
metallic crystal are filled with smaller atoms
 Carbon steel
Great test question…