Dihydrogen monoxide? It is in water sources everywhere… It is responsible for many deaths every year…

Monatomic ions consist of a single atom with a positive or negative charge.

Positive ions result from the loss of one or more valence electrons.

negative ions result from the gain of one or more valence electrons.

Cations

When the metals in Groups 1A, 2A, and 3A lose electrons, they form cations with positive charges equal to their group number.

The names of the cations of the Group 1A, Group 2A, and Group 3A metals are the same as the name of the metal, followed by the word ion or cation.

Na Na+

Sodium atom sodium cation or sodium ion

Group1A = 1 valence e- = +1 ion

These elements have ionic charges that can be obtained from their group numbers.

Al3+ 3e-

Non-metals gain electrons.

Anion charge = group number - 8

Anion names start with the stem of the element name and end in -ide.

O O oxygen atom oxide

ion

2-

These Group A elements form anions.

Some transition metals can form more than one ion.

The charges of these transition metal cations must be specified because there is more than one possible charge.

These colorful solutions contain the transition metal ions Co3+, Cr3+, Fe3+, Ni2+, and Mn2+.

Many transition metal compounds are colored and can be used as pigments.

Two methods are used to name the ions of transition metals.

•The Stock system

•The classical method

In the Stock system, a Roman numeral in parentheses is placed after the name of the element to indicate the numerical value of the charge.

FeCl3 iron(III) chloride

FeCl2 iron(II) chloride

In an older less useful method, the latin name of the element is used to form the root name for the ion.

Conceptual Problem 9.1

Polyatomic ions, are composed of more than one atom.

The names of most polyatomic anions end in -ite or -ate.

These models show the structures of four common polyatomic ions.

Names and Formulas of Some Common Polyatomic Ions

Polyatomic ions are covalently bound groups with an overall charge.

NaHCO3

Sodium hydrogen carbonate can relieve an upset stomach.

HCO3–, HPO4

2–, and H2PO4– ions in

your blood are critical for your health.

Fertilizers contain HPO42– and H2PO4– ions.

A binary compound is composed of two elements and

can be either ionic or molecular.

Ionic compounds are named differently than molecular(covalent) compounds.

When naming ionic compounds, state the cation first then the anion.

KNO3

K+ NO3-

potassium nitrate

TiO2

Ti4+ O2-

titanium(IV) oxide

Watch out for elements that make multiple

ions!!- They need (charge)

Look out for polyatomic

ions!! More than 1 non-metal

Tin(II) flouride, or SnF2, is added to toothpastes to prevent cavities.

Tin(IV) sulfide, or SnS22,, is used in glazes for porcelain fixtures and dishes.

Hematite, a common ore of iron, contains iron (III) oxide. The balanced formula is Fe2O3.

Writing Formulas for Ionic Compounds

Write the symbol of the cation and then the anion. Add whatever subscripts are needed to balance the charges.

Al3+ and O2- ions make Al2O3 crystals.

Compounds With Polyatomic Ions

calcium cation– Ca2+

polyatomic nitrate anion– NO3–

Two nitrate anions are needed to balance the 2+ charge of the calcium cation.

calcium nitrate is Ca(NO3)2.

Parenthesis are needed to show more than one polyatomic ion.

Lead(II)sulfate is an important component of an automobile battery.

1. When metals from groups 1A, 2A, and 3A form cations, the charge on the ion is equal to

a. 8 minus the group number.

b. the group number minus 8.

c. the period number.

d. the group number.

9.1 Section Quiz.

2. Which of the following are positively charged polyatomic ions?

a. (I) ammonium ion

b. (II) perchlorate ion

c. (III) ferric ion

a. I only

b. II only

c. III only

d. I and III

3. If the name of an ion ends in -ite or -ate, the ion is a

a. polyatomic cation.

b. polyatomic anion.

c. transition metal cation.

d. monatomic anion.

1. The correct name for CrCl3 is

a. chromium chlorine.

b. chromium(III) chloride.

c. chromium(II) chloride.

d. chromium chloride.

9.2 Section Quiz

2. What is the correct formula for strontium nitride?

a. Sr3N2

b. SrN2

c. Sr2N3

d. Sr3N

3. Which one of the following compounds is named correctly?

a. sodium chlorite, NaClO

b. potassium nitrate, KNO2

c. sodium acetate, NaC2H3O2

d. lithium sulfate, Li2SO3