Naming of Ionic Compounds

Packet #15

Introduction

• An atom that has lost/gained electrons is considered to be an ion• Cation

• Lost one or more electrons• Positive charge

• Anion• Gained one or more electrons

• Negative charge

NAMING IONS

Introduction

• Monatomic ion consist of a single atom with a positive or negative charge resulting from the loss or gain of one or more electrons.

NAMING IONSAnions

Introduction

• Remember, anions are formed when an atom gains one or more electrons while cations are formed when an atom has lost one or more electrons.

• The number of electrons added /lost determines what the charge the atom has.

Anions

• The charge of any ion of Group A nonmetal is determined by subtracting 8 from the group number.

Monatomic Anion—Naming• The name of simple anions

is obtained by adding –ide to the root of the atom name.• Flourine

• F + e- = F-

• Flouride

• Bromine• Br + e- = Br-

• Bromide

• Anions that have gained two electrons, oxide (O2-) and sulfide (S2-) for example, are named in the similar manner.

NAMING IONSCations

Groups 1, 2 & 3

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

• The metals of Group 1A, 2A and 3A consistently form cations of 1+, 2+ and 3+ respectively.

Monatomic Ion—Cation Naming

• Simple cations borrow their names from the names of the elements.• K+

• Potassium ion

• Ca+

• Calcium ion

IONS OF TRANSITION METALS

Ions of Transition Metals

• Many of the transition atoms form more than one cation with different ionic charges.• The charges of the

cations of many transition atoms must be determined from the number of electrons that are lost.

Ions of Transition Metals I

• Iron• Forms two common

cations• Fe2+

• Iron II ion• Fe3+

• Iron III ion

• Tin, lead, copper, zinc and mercury• Can also produce

cations of different charges.

Naming Transition Elements Ions

• An older, useful method for naming cations, uses a root word with different suffixes at the end of the word.

• Ferrum is Latin for iron…therefore the root for iron is ferr-.

Naming of Transition Elements Ions II

• The suffix -ous is used to name the cation with the lower of the two cations.

• The suffix –ic is used to name the cation with the higher of the two cations.• Ferrous iron

• Fe2+

• Ferric iron• Fe3+

Naming of Transition Elements Ions III

POLYATOMIC IONS

Polyatomic IonsIntroduction

• A polyatomic ion is composed of more than one atom.

• Polyatomic ions are tightly bound group of atoms that behave as a single unit and carry a charge.

Naming of Polyatomic Ions I

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

Naming of Polyatomic Ions II• Sometimes the same

two or three elements combine in different ratios to form polyatomic ions.• Notice the endings• Examine the charge• Note the number of

oxygen atoms that the ion contain.

• There should be a pattern.

Naming of Polyatomic Ions III

• The charge in each polyatomic ion in a given pair is the same.• The -ite ending

indicates the polyatomic with one less oxygen atom than the -ate ending.• However, it does not

tell how many oxygen atoms there are in the ion

Common Polyatomic Ions

System of Writing Formula of an Ionic Compound• Write the symbol and

charges for the cation and the anion

• Write the symbols for the ions side by side, beginning with the cation.

• To determine how to get a neutral compound, look for the lowest common multiple of the charges on the ions.• For example, the lowest

common multiple of 3 and 2 is 6.

• Fe3+

• Iron (III)• O2-

• Oxide• The lowest common

multiple of 3 and 2 is 6.• Therefore, the formula

should indicate six positive charges and six negative charges.

• Fe2O3

• For 6 positive charges, you need two Fe2+

• For 6 negative charges, you need three O2-

System of Naming an Ionic Compound (Binary Ionic Compounds)

• The name is made up of two words• The name of the

cation• Followed by the

name of the anion

• NaCl• Cation

• Sodium• Anion

• Chloride• Sodium chloride

• CuCl2

• Cation• Copper (II)

• Anion• Chloride

• Copper (II) chloride

• Al2S3

• Cation• Aluminum

• Anion• Sulfide

• Aluminum sulfide

System of Naming Polyatomic Ions

• Name the cation• Recall that a cation

is simply the name of the element

• Name the anion• Remember, one

must determine the charge of the anion to determine whether it receives–ite or –ate.

• K2CO3

• Cation• Potassium

• Anion• Has a charge of -2

• CO3-2 has a name of

carbonate• The polyatomic

ion’s name is thus potassium carbonate.

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