Naming Ionic Compounds

Metals Joining with Nonmetals or Polyatomics

Ionic Compounds• Positive Ion is called a CATION. They are metals.

• Negative Ion is called an ANION. They are non-metals.

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Give the names of the following ions:

Ba2+ Al3+ K+

_________ __________ _________

N3 O2 F

_________ __________ _________

P3 S2 Cl

_________ __________ _________

Learning Check

Ionic Compounds• Notice the cross

over of Charges• The Cation is

always written FIRST, Anion Second.

• Ionic compounds are made up of metals and non-metals, the metal is written FIRST.

Formation of Ionic Compounds

Crossing Rule

Ca+2 + Cl-1 CaCl2

But you MUST make sure to check to see if the whole number ratios canbe REDUCED. If they can, you must reduce them.

Example of reducing:• Cr4+ O2-

• If you just cross you get Cr2O4 but this would NOT be the correct formula for chromium (IV) oxide.

• The correct formula is CrO2

Naming Rules• Step 1: The name of the metal is written first, the

same way it is written on the periodic table• Step 2: Write the name of non-metal second, BUT

change the ending of the element to –ide.• Step 3: Remember the crossing rule and

remember to reduce!

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Formula Ions Name Cation Anion

NaCl Na+ Cl– sodium chloride

K2S K+ S2– potassium sulfide

MgO Mg2+ O2– magnesium oxide

CaI2 Ca2+ I– calcium iodide

Al2O3 Al3+ S2– aluminum sulfide

Examples of Ionic Compounds with

Two Elements

Multiple Ionic Charges & Names

• Some Transition metals can have more than one charge and therefore more than one name.

Element name Symbol

Ionic Charges

Roman numeral

Copper Cu +1, +2 I, II

Iron Fe +2, +3 II, III

Lead Pb +2, +4 II, IV

Tin Sn +2, +4 II, IV

How do I know if a metal is multi-valanced

(mulitiple ionic charges)?

• Look at you table of ions!

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Transition Metals Form Positive

IonsMost transition metals and Group 4(14) metals, Form 2 or more positive ions Zn2+, Ag+, and Cd2+ form only one ion.

When writing the names

• Write the name of the element followed by the Roman numeral.

• EX: Cu2+ is written Copper(II)• So, what is the name of Fe3+ ?• How would you write the name of PbCl4?

Metals with Variable Charge

The names of transitionmetals with two or morepositive ions (cations) use aRoman numeral after thename of the metal to identifyionic charge.

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Examples of Names of Compounds

with Variable Charge Metals

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Naming FeCl2

STEP 1 Determine the charge of the cation from the anion.

Fe ion + 2 Cl– = Fe ion + 2– = 0

Fe ion = 2+ = Fe2+

STEP 2 Name the cation by the element name, and use a Roman numeral to show its charge.

Fe2+ = iron(II)

STEP 3 Write the anion with an ide ending. chloride

STEP 4 Name the cation first, then the anion.

iron(II) chloride

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Naming Cr2O3

STEP 1 Determine the charge of cation from the anion. 2Cr ions + 3O2– = 2Cr ions + 3(2–)

= 2Cr ions + 6– = 0

2Cr ions = 6+ Cr ion = 3+ = Cr3+

STEP 2 Name the cation by the element name, and use a Roman numeral to show its charge.

Cr3+ = chromium(III)

STEP 3 Write the anion with an ide ending. oxide

STEP 4 Name the cation first, then the anion.

chromium (III) oxide

Polyatomic Ionic Compounds

What is a polyatomic ion?Polyatomic ions: groups of atoms that tend to stay together and carry an overall ionic charge. They still need two parts!

Table of Common Polyatomic

IonsName of polyatomicion

Ion fomula Ionic Charge

Nitrate NO3- -1

Hydroxide OH- -1

Bicarbonate (hydrogen carbonate)

HCO3- -1

Chlorate ClO3- -1

Carbonate CO3-2 -2

Sulfate SO4-2 -2

Phosphate PO4-3 -3

Ammonium NH4+ +1

Polyatomic Compound Formulas

• Formulas for polyatomic compounds is determined the same way as ionic compounds. Cation first, Anion second, cross over rule

• But… brackets may be required!!!

Al+3 + CO3-

2

Al2(CO3

)

Ammonium Ion• The only positively charged polyatomic ion.

• NH4+ ammonium ion

• Ammonium nitrate : ammonium ion NH4+

nitrate ion NO3-

• NH4NO3

• Because this ion has a positive charge, it WILL come first.

Naming Polyatomic Compounds

• Step 1: Write the name of the metal first.

• Step 2: Write the name of the polyatomic ion second.

• NaH2CO3

• Sodium hydrogen carbonate or sodium bicarbonate

NOT sodium hydrogen carbon oxide!!!!!!!

Hydrates

A hydrate is a compound that has a specific number of water molecules within its solid structure.

For example, in its normal state, copper(II) sulfate has five water molecules associated with it.

Systematic name: copper(II) sulfate pentahydrateFormula: Cu(SO)4 ∙ 5H2O

Some other hydrates areBaCl2 ∙ 2H2OLiCl ∙ H2OMgSO4 ∙ 7H2OSr(NO3)2 ∙ 4H2O

Hydrates

When the water molecules are driven off by heating, the resulting compound, Cu(SO)4, is sometimes called anhydrous copper(II) sulfate.

Anhydrous means the compound no longer has water molecules associated with it.

Pg 89

The Hydrate of coppersulfate is the pentahydrate,and the anhydrous coppersulfate will absorb water to form the Hydrate.

CuSO4 5 H2O.

Familiar Inorganic Compounds