Names and Formulas Names and Formulas for Ionic Compoundsfor Ionic Compounds

Chemistry Fall 2009Chemistry Fall 2009

Section 8.3Section 8.3

Formulas for Ionic Formulas for Ionic CompoundsCompounds

represented by a formula providing represented by a formula providing the simplest ratio of the ions involved the simplest ratio of the ions involved called a called a formula unitformula unit– KBr = potassium bromide; 1:1 ratioKBr = potassium bromide; 1:1 ratio

# e- gained by the nonmetallic atoms # e- gained by the nonmetallic atoms must equal the # e- lost by the must equal the # e- lost by the metallic atoms; overall charge = 0metallic atoms; overall charge = 0– MgClMgCl2 2 = (1) Mg= (1) Mg2+2+ ion & (2) Cl- ions ion & (2) Cl- ions

Determining Charge – Determining Charge – monatomic ionsmonatomic ions

Common Ions Based on GroupsCommon Ions Based on Groups

GroupGroup Atoms that Atoms that commonly form ionscommonly form ions

ChargCharge on e on ionsions

1A1A H, Li, Na, K, Rb, CsH, Li, Na, K, Rb, Cs 1+1+

2A2A Be, Mg, Ca, Sr, BaBe, Mg, Ca, Sr, Ba 2+2+

3B3B Sc, Y, LaSc, Y, La 3+3+

5A5A N, P, AsN, P, As 3-3-

6A6A O, S, Se, TeO, S, Se, Te 2-2-

7A7A F, Cl, Br, IF, Cl, Br, I 1-1-

Oxidation Numbers and Oxidation Numbers and Writing Ionic Compound Writing Ionic Compound

FormulasFormulasOxidation number – Oxidation number – the oxidation number or the oxidation number or oxidation state of an element in an ionic oxidation state of an element in an ionic compound equals the number of electrons compound equals the number of electrons transferred from an atom of the element to form transferred from an atom of the element to form the ion.the ion.

The oxidation numbers are used to determine The oxidation numbers are used to determine the formulas for the ionic compounds they form. the formulas for the ionic compounds they form.

Oppositely charged ions combine chemically in Oppositely charged ions combine chemically in definite ratios to form a compound that has no definite ratios to form a compound that has no charge.charge.

If you add the oxidation number of each ion If you add the oxidation number of each ion multiplied by the number of these ions in a multiplied by the number of these ions in a formula unit, the total must be 0.formula unit, the total must be 0.– Example: K has a charge of +1 and O has a charge of -Example: K has a charge of +1 and O has a charge of -

2. If the charges are not the same, subscripts must be 2. If the charges are not the same, subscripts must be determined to indicate the ratio of (+) to (-) ions. Kdetermined to indicate the ratio of (+) to (-) ions. K22OO

– H/O Counting Atoms WorksheetH/O Counting Atoms Worksheet

Charge of Transition Charge of Transition MetalsMetals

P. 222 in textbook: Common Ions of P. 222 in textbook: Common Ions of Transition MetalsTransition Metals

Charge of a monatomic ion = Charge of a monatomic ion = oxidation numberoxidation number

The number of e- transferred from an The number of e- transferred from an atom of the element to form the ionatom of the element to form the ion– Na+ and Cl-Na+ and Cl-– Positively charged ion of a metal and Positively charged ion of a metal and

negatively charged monatomic ion of a negatively charged monatomic ion of a nonmetalnonmetal

– Oxidation state of Na is +1; Cl is 1-Oxidation state of Na is +1; Cl is 1-– Transition metals can form several Transition metals can form several

different positive ions based on the different positive ions based on the variance in ionic charges of atoms in the variance in ionic charges of atoms in the groupsgroups

Now you try…Now you try…

Write the correct formula for the ionic Write the correct formula for the ionic compound composed of the following compound composed of the following pairs of ions:pairs of ions:

a. potassium and iodidea. potassium and iodide b. magnesium and chlorideb. magnesium and chloride c. aluminum and bromidec. aluminum and bromide d. cesium and nitrided. cesium and nitride e. barium and sulfidee. barium and sulfideH/O Writing Formulas PracticeH/O Writing Formulas Practice

Polyatomic IonsPolyatomic Ions

Polyatomic ionsPolyatomic ions = ions made up = ions made up of more than one atomof more than one atom– Charge given applies to the entire Charge given applies to the entire

group of atomsgroup of atoms– Exists as a unit, never change Exists as a unit, never change

subscripts of the atoms within the ionsubscripts of the atoms within the ion– If more than one is needed, place If more than one is needed, place

parentheses around the ion and write parentheses around the ion and write the appropriate subscript outside the the appropriate subscript outside the parentheses Mg(ClOparentheses Mg(ClO33))22

Polyatomic Ions you Polyatomic Ions you should memorize…should memorize…

ammonium (NHammonium (NH44)) sulfite (SO sulfite (SO332-2-))

nitrite (NOnitrite (NO22--)) sulfate (SO sulfate (SO44

2-2-))

nitrate (NOnitrate (NO33--)) phosphate (PO phosphate (PO44

3-3-))

hydroxidehydroxide (OH(OH--)) carbonate (CO carbonate (CO332-2-))

chlorite (ClOchlorite (ClO22--)) chlorate (ClO chlorate (ClO33

--))

Now you try…Now you try…

Determine the correct formula for Determine the correct formula for the ionic compound composed of the ionic compound composed of the following pairs of ions:the following pairs of ions:

a. sodium and nitratea. sodium and nitrate b. calcium and chlorateb. calcium and chlorate c. aluminum and carbonatec. aluminum and carbonate d. potassium and chromated. potassium and chromate e. magnesium and carbonatee. magnesium and carbonate

Naming Ions and Ionic Naming Ions and Ionic CompoundsCompounds

Oxyanion Oxyanion = polyatomic ion = polyatomic ion composed of an element bonded to composed of an element bonded to one or more oxygen atomsone or more oxygen atoms

1.1. The ion with more oxygen atoms is The ion with more oxygen atoms is named using the root of the named using the root of the nonmetal plus the suffix –ate.nonmetal plus the suffix –ate.

2.2. The ion with fewer oxygen atoms is The ion with fewer oxygen atoms is named using the root of the named using the root of the nonmetal plus the suffix –ite.nonmetal plus the suffix –ite.

• Ex. NOEx. NO33- - NONO

22- - SOSO44

2-2- SO SO332-2-

nitrate nitrite sulfate sulfitenitrate nitrite sulfate sulfite

Oxyanions forming Oxyanions forming with halogenswith halogens

1.1. The oxyanion with the greatest The oxyanion with the greatest number of oxygen atoms is named number of oxygen atoms is named using the prefix per-, the root of the using the prefix per-, the root of the nonmetal, and the suffix –atenonmetal, and the suffix –ate

2.2. The oxyanion with one less oxygen The oxyanion with one less oxygen atom is named with the root of the atom is named with the root of the nonmetal and the suffix –atenonmetal and the suffix –ate

3.3. The oxyanion with two fewer oxygen The oxyanion with two fewer oxygen atoms is named using the root of the atoms is named using the root of the nonmetal plus the suffix -itenonmetal plus the suffix -ite

Oxyanions forming Oxyanions forming with halogens cont.with halogens cont.

4. The oxyanion with three fewer 4. The oxyanion with three fewer oxygen atoms is named using the oxygen atoms is named using the prefix hypo-, the root of the prefix hypo-, the root of the nonmetal, and the suffix –itenonmetal, and the suffix –ite

ClOClO44-- ClO ClO33

-- ClO ClO22-- ClO ClO--

perchlorate chlorate chloriteperchlorate chlorate chlorite hypochloritehypochlorite

Naming Ionic Naming Ionic CompoundsCompounds

1.1. Name the cation first and the Name the cation first and the anion second – CsBranion second – CsBr

2.2. Monatomic cations use the Monatomic cations use the element name – Cs is Cesiumelement name – Cs is Cesium

3.3. Monatomic anions take their Monatomic anions take their name from the root of the name from the root of the element name plus the suffix –element name plus the suffix –ide – CsBr (bromide)ide – CsBr (bromide)

Naming Ionic Naming Ionic Compounds Cont…Compounds Cont…

4. Group 1A and group 2A metals have 4. Group 1A and group 2A metals have only one oxidation number. Transition only one oxidation number. Transition metals and metals on the right side of metals and metals on the right side of the periodic table often have more the periodic table often have more than one oxidation number – Fethan one oxidation number – Fe22OO3 3 is is named iron (III) oxidenamed iron (III) oxide

5. If the compound contains a 5. If the compound contains a polyatomic ion, simply name the ion.polyatomic ion, simply name the ion.

NaOH is sodium hydroxideNaOH is sodium hydroxide

Now you try…Now you try…

Name the following compounds:Name the following compounds:

a. NaBra. NaBr

b. CaClb. CaCl22

c. KOHc. KOH

d. Cu(NOd. Cu(NO33))22

e. Age. Ag22CrOCrO44

H/O Naming Ionic CompoundsH/O Naming Ionic Compounds

Complete the following Complete the following table…table…

OxideOxide ChlorideChloride SulfateSulfate PhosphaPhosphatete

PotassiuPotassiumm

BariumBarium

AluminuAluminumm

AmmoniuAmmoniumm