IonicCompounds and Metals
Chapter 7
Vocabulary Ch. 7.1
Chemical bond Cation Anion
2
Ch. 7.2 Ionic bond Ionic compound Binary
compound Crystal lattice Electrolyte Lattice energy
Objectives Define a chemical bond Describe how ions form Identify ionic bonding and the
characteristics of ionic compounds Name and write formulas for
binary compounds Polyatomic ion containing compounds Compound with metals that have multip
le oxidation states Hydrates
3
4
Forming Compounds The Octet Rule: Atoms become stable
by having 8 electrons in their outer energy level (2 for smaller atoms) Similar arrangement of valence
electrons for element in the same group. (Ex: ns1 for alkali metals)
Electron arrangements determines chemical properties
Presents a model of chemical stability When they have gotten 8 electrons they
have achieved NOBLE GAS CONFIGURATION
5
Forming Compounds
atoms collide with enough energy
outer electrons move to achieve a stable octet of valence electrons (noble gas configuration).
atoms formed a new compound Total # of e- must remain the
same. Electrons are particles of matter.
6
Forming Compounds Transfer of Electrons
.. ..Na· + ·Cl: [Na]+ + [:Cl:]-
˙˙ ˙˙
7
8
9
Lattice Energy
Ionic compounds consist of a crystal lattice of positive and negative ions, which is a repeating pattern of ions.
= Cl-
= Na+
10
Lattice Energy
The lattice energy is the energy required to separate the ions from their crystalline solid state.
Increases with decreasing ionic size.
Increases with increasing ionic charge.
11
Lattice energy decreases as anion gets bigger!!
Lattice energy is large due to +2 and -2 Charges; decreases as ions get larger.
12
Lattice EnergyPhysical Properties of ionic compounds: The melting point increases as
lattice energy increases. Solutions are electrolytes, which
conduct an electric current. Force applied to crystals causes them
to shatter.
13
Vocabulary Ch. 7.3
Formula UnitMonoatomic ionOxidation NumberPolyatomic ion
14
Names and Formulas
Rules for naming binary compounds
1. Name the cation first. This is usually a metal. Use element name.
2. Then name the anion using the 1st syllable of the of the element name and then end in –ide.
Example: Potassium Chloride (KCl)
Magnesium Oxide (MgO)
15
Binary Compound Naming PracticeFormula NaF Al2S3
CaO Mg3N2
CaH2
Name
16
Predicting Charge on Ions
Can you predict the charge on an ion depending on where it is in the periodic table?
Yes, of course. Group numbers can help predict many charges. For groups 1 & 2 – they lose electrons
and become positive Group 13 – loses 3 electrons and are
generally positive Groups 15 – 17 gain electrons and
become negative in ions.17
Predicting Charge on Ions
The charge on a monoatomic ion is the
Oxidation number
Again, oxidation number for many elements in the main group (Groups 1 & 2, 13-18) can be predicted by looking at the group number.
18
Rules For Writing Ionic Compound Formulas
1. Write cation symbol first. (Same as we did in naming them.)
2. Write anion symbol second.3. Add subscripts such that the sum of
the charges is zero.4. Write the simplest ratio of ions.
This is the formula unit.
19
Writing Ionic Formula
Example: What is the formula for Aluminum Oxide? What is charge on aluminum when it is
an ion? What is charge on oxygen when it is an
ion (oxide)? How do we get the charges to balance?
20
Use it backward—knowing compoundFigure out charges
Method of “Cross-Multiplying”
What would be the subscriptsto make the Sum = 0?
Drop the signs and make the numbers subscripts
21
Examples of Writing Formulas
(Binary Compounds)Name of Compound Lithium oxide
Lithium ions and oxide ions Li+ O2-
Calcium chloride Calcium ions and chloride ions
Ca2+ Cl-
Magnesium nitridemagnesium ions and nitride ions
Mg2+ N3-
Formula of Compound
22
Practice Writing Binary Compound FormulasName of
Compound Lithium iodide Beryllium
chloride Calcium oxide Sodium oxide Strontium
sulfide Calcium
phosphide
Formula of Compound
23
Compounds of Metals with Multiple Oxidation States
(Multivalent Metals) Includes metals in Groups 3 through
12 of the periodic table And the representative metals in
Groups 13 & 14 (Commonly Sn & Pb, but also Ga, In, and Tl)
They have more than one
Oxidation State So they can form more than one
type of positive ion.24
Compounds of Multivalent Metals
For Example:Copper can exist as Cu+ and
Cu2+
Iron can exist as Fe2+ and Fe3+
Exceptions: Zn and Ag. Zinc only forms a Zn2+ ion Ag only forms a Ag+ ion
25
Compounds of Multivalent Metals
How do chemists distinguish the names of compounds formed these metals?
We use Roman numerals in parenthesis after the name of the element.
Copper Ion
Chloride Ion
Formula Name
Cu+ Cl- CuCl Copper (I) Chloride
Cu2+ 2Cl- CuCl2 Copper (II)
Chloride26
Compounds of Multivalent Metals
27
Compounds of Multivalent Metals
28
Formulas of Multivalent Metals
How to write a formula containing one of these metals. First, look at the name.
Example: if it is Manganese (III) it means that it’s Mn3+
The roman numeral is the oxidation number of the ion, not how many there are!!!!
Then, you can balance charges as before.
Example: MnCl3
Manganese is 3+ and chloride is always 1-.
29
Writing Names of Multivalent Metal
Compounds If your given a formula, how do you
figure out the name? Determine the charge on the metal
ion. Look at the negative ion. Figure out what was needed to make
the compound neutral Example: FeCl3
30
Compounds of Multivalent Metals
Given name or formula Iron(II) oxide
MnF3
Nickel(II) chloride
PbS2
Determine formula or name
31
What is the oxidation number of Zinc when it’s an ion?
a) 1+ or 2+
b) 2+ always
c) 1+ always
d) 1- or 2-
32
What is the formula for iron(II) oxide?
a) Fe2O
b) FeO2
c) Fe2O2
d) FeO
33
What is the correct name of MnF3?
a) Manganese (I) fluorideb) Magnesium (I) fluoridec) Manganese (III) fluorided) Magnesium (III) fluoride
34
What is the correct formula for nickel(II) chloride?
a) Ni2Cl
b) NiC2
c) NiCl2d) Ni2Cl2
35
What is the name of PbS2?
a) Lead (IV) sulfide
b) Lead (I) sulfide
c) Lead (II) sulfide
d) Lead (III) sulfide
36
Polyatomic Ions
Ions can contain more than one element.
An ion with two or more different elements is a
Polyatomic Ion In polyatomic ions, the atoms are
covalently bonded and the atoms share electrons.
Individual atoms have no charge, but the group has an overall charge.
Example: SO42- (Sulfate)
37
Common Polyatomic IonsName of Ion Formula Charg
eAmmonium NH4
+ 1+
Hydrogen carbonate
(bicarbonate)
HCO3- 1-
Hydrogen sulfate
HSO4- 1-
Acetate C2H3O2- 1-
Nitrite NO2- 1-
Nitrate NO3- 1-
Cyanide CN- 1-Hydroxide OH- 1-
38
Common Polyatomic Ions
Name of Ion Formula Charge
Dihydrogen phosphate
H2PO4- 1-
Permanganate MnO4- 1-
Carbonate CO32- 2-
Sulfate SO42- 2-
Sulfite SO32- 2-
Oxalate C2O42- 2-
Monohydrogen phosphate
HPO42- 2-
Dichromate Cr2O72- 2-
Phosphate PO43- 3-
39
Compounds Containing Polyatomic Ions
1. When there is more than one polyatomic ion, treat it as if it were a single ion by keeping it together as a unit using parenthesis.
2. Write a subscript outside the parenthesis to show how many units there are of polyatomic ion.
3. Remember that the sum of the charges must equal zero.
40
41
Examples of Writing Formulas
(w/Polyatomic Ions)Name of Compound Calcium nitrate
Calcium ions and nitrate ions Ca2+ NO3
1-
Sodium carbonateSodium ions and carbonate ions
Na+ CO32-
Lead(II) Phosphate lead 2+ ions and phosphate ions
Pb2+ PO43-
Formula of Compound
42
Naming Polyatomic Compounds
from formulas1. Positive ion (usually a metal) is
named first as before.2. Negative polyatomic ion name
as listed in the chart is second. Note: If you see more than one
element after the metal the rest is a polyatomic ion. Look for that group in the chart.
43
Polyatomic Ion Practice
Given name or formula: NaHCO3
Lithium Acetate Ca(CN)2
Copper(II) Hydroxide K2Cr2O7
Fe(HCO3)3
Ammonium Chloride
Determine formula or name
44
What is the formula for zinc arsenate?
Note: You have to type this in. Hit the ‘Shift’ key (lower right) to
get capital letters. If you need parenthesis, hit sym 4
for ‘(‘ and sym 5 for ‘)’.
45
Ch. 7.4 Vocabulary
Ch. 10.5 Hydrate (page
351)
Ch. 7.4 Electron Sea
model Delocalized
electron Metallic Bond Alloy Interstitial alloy Substitutional
Alloy46
Compounds of Hydrates (Ch. 10.5)
Hydrate – when there is a specific amount of water in the crystal of a compound.
The water molecules are part of the crystal structure of the ionic compound.
Many compounds become hydrates by absorbing water from the air. The water then becomes part of its structure.
Many of them are used as drying agents (desiccants).
47
Compounds of Hydrates
When writing a formula for a hydrated compound use a dot (•) followed by the number of water molecules.
Example: CaCl2•2H2O
This means that this hydrated chloride compound has 2 molecules of water for each formula unit of calcium chloride. 48
CaCl2•2H2O
Ca+2 Cl-Cl- Cl-
Water
Water
-
-
Compounds of Hydrates
CaCl2•2H2O This means that this hydrated chloride
compound has 2 molecules of water for each formula unit of calcium chloride.
You would call the compound Calcium chloride dihydrate.
Rule: Follow the regular name of the compound with the word “hydrate.” The prefix before “hydrate” tells you how many water molecules there are.
50
Prefixes for HydratesMolecules of Water Prefix
1 Mono-2 Di-3 Tri-4 Tetra-5 Penta-6 Hexa-7 Hepta-8 Octa-9 Nona-10 Deca- 51
Hydrate Compound Practice
Given Name or Formula
MgSO3•6H2O
Strontium oxalate monohydrate
Ni3(PO4)2•7H2O
Lead(II) acetate trihydrate
Determine the Formula or Name
52
Compounds of Hydrates
Hydrates can also lose water molecules, usually by heating.
They may even have a different color than the hydrated compound.
When they lose their water molecules, they become anhydrous (without water). 53
Ch. 7.4 - Metal Bonding – Electron Sea Model
There are not enough electrons for the metal atoms to be covalently bonded to each other.
We use a delocalized model for electrons in a metal
54
Delocalized Electrons in a Metal
The metal nuclei are seen to exist in a sea of electrons.
No electrons are localized between any two metal atoms.
Therefore, the electrons can flow freely through the metal.
Without any definite bonds, the metals are easy to deform (and are malleable and ductile).
The more delocalized e-, the harder and stronger the metal.
55
56
Delocalized Model for Electrons in a Metal
Melting Point
57
Malleability
58
Metals, above, compared to ionic compounds, below.
Alloys Alloys are homogeneous mixtures,
metal solutions, really. Substitutional alloys:
atoms must have similar atomic size, elements must have similar bonding
characteristics. Interstitial alloys:
one element much smaller than the other in order to fit into the interstitial sites, e.g. a nonmetal.
The alloy is much stronger than the pure metal (increased bonding between nonmetal and metal).
Example steel (contains up to 3% carbon).
59
Alloys
60
Common Alloys
61