LECTURE 5 CHM 151 ©slg

TOPICS:

1. Naming Cations2. Naming Anions3. Naming Ionic compounds4. Naming Molecular Binary Compounds

NAMING MOLECULES AND COMPOUNDS

There are many rules for naming many types of compounds: To name any compound, you must first recognize its “type.”

“Guidelines”:

If the compound formula starts with a nonmetal or metalloid,it is a molecular type compound

If the formula starts with a metal, consider it an ionic compound, If the formula starts with H, it is an acid

We’ll name in this lesson two specific types:

“binary molecules” (two non-metals in formula ) CO2 PCl3 SO3 AsF3

“ionic salts and bases” ( cation / anion combinations)

cation: some metal ion or NH4+

anion: OH- or O2- (a “base”) all other anions: (“salts”)

K2SO4 NH4Cl NaOH MgO FeBr3

Before naming ionic compounds, let’s review cations and anions, and examine charges and formulas we need to know.....

POSITIVE IONS: Cations

CATIONS: positively charged ions; monoatomic cations are formed from metals which have LOST one or more electrons in compound formation:

- 1 eNa (11p, 11e) --------> Na+ (11p, 10e) (all Group 1A)

-2eCa (20p, 20e) --------> Ca2+ (20p, 18e) (all Group 2A)

1A 2A 3B 1B 2B 3A12 Li Be3 Na Mg Al4 K Ca Zn5 Rb Sr Ag Cd6 Cs Ba7

Metals Forming One Cation Only (Memorize!)

• Charge will be same as column or “Group Number”

• 3B elements form only one charge but aren’t on “memory list”

“One Charge Only”

1+ 2+

1+

3+2+ 3+

1A 2A 3B 1B 2B 3A1

2 Li+ Be2+

3 Na+ Mg2+ (3+) Al3+

4 K+ Ca2+ (3+) Zn2+

5 Rb+ Sr2+ (3+) Ag+ Cd2+

6 Cs+ Ba2+ (3+)

Naming Cations: Fixed Charge Metals

When the metal in the salt or base exhibits only one charge and forms only one cation,the name of the cation is identical with that of the metal:

Na+ sodium cation Mg2+ magnesium cationAl3+ aluminum cation Ag+ silver cation

Metals Forming Several Cations

All other common metals form cations resulting from the loss of a variable number of electrons (depending on the circumstances of the reaction).

An examination of electronic structure (Unit 3) willjustify all charges, single or multiple; now we simply must recognize “which is which”.........

1A 2A 3B 4B 5B 6B 7B 8B 8B 8B 1B 2B 3A 4A 5A12 Li Be3 Na Mg Al4 K Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga5 Rb Sr Y Zr Nb Mo Ru Rh Pd Ag Cd In Sn6 Cs Ba La Hf Ta W Re Os Ir Pt Au Hg Tl Pb Bi

Naturally Occurring, Non-Radioactive Metals

1A 2A 3B 4B 5B 6B 7B 8B 8B 8B 1B 2B 3A 4A 5A12 Li Be3 Na Mg Al4 K Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga5 Rb Sr Y Zr Nb Mo Ru Rh Pd Ag Cd In Sn6 Cs Ba La Hf Ta W Re Os Ir Pt Au Hg Tl Pb Bi

Common Metals, Fixed vs Variable Charge

Metals which form single cation

Metals which form several cations

Typically Encountered Cations, Variable Charge Metals

Cr2,3+

Fe2,3+

Co2,3+

Ni, Mn 2+

Cu1,2+

Hg2+, Hg22+

Sn, Pb 2+

Bi3+

Maximum (if not always common) charge on all metals isgiven by group number...

Naming Cations: Metals with Variable Charges

When a metal is known to form several differentcations of different charges, then the name of the cation must include a Roman Numeral indicatingthe charge of the ion:

Fe2+ Iron(II) cation Cu+ Copper(I) cationFe3+ Iron(III) cation Cu2+ Copper(II) cation

Sn2+ Tin(II) cation Bi3+ Bismuth(III) cation

NEGATIVE IONS: Anions

Monoatomic ANIONS:

Single nonmetallic atoms which have gained one or more electrons in a chemical reaction and become negatively charged ions : +3eN (7p, 7e) --------> N3- (7p, 10e) (all Group 5A) +2eO(8p, 8e) --------> O2- (8p, 10e) (all Group 6A) +1eF (9p, 9e) --------> F1- (9p, 10e) (all Group 7A)

1A 5A 6A 7A

1 H-

2 N3- O2- F-

3 P3- S2- Cl-

4 Se2- Br-

5 I-

6

3-

Monoatomic Anions: Name, Charge

2- 1-

Hydride Nitride Oxide Phosphide Sulfide Selenide

FluorideChlorideBromideIodide

“ide”“ide”

FORMING IONIC COMPOUNDS

Na+ Cl- NaCl

Na+ S2- Na2S

Na+ P3- Na3P

Ba2+ Cl- BaCl2

Ba2+ S2- BaS

Ba2+ P3- Ba3P2

Make sure charges balance; cross multiply whencation and anion charges are different:

GROUP WORK

• CATION, ANION

• Mg2+ H -

• Fe3+ S2-

• Al3+ P3-

• Cd2+ F -

• Mn2+ I -

• FORMULA, NAME

POLYATOMIC IONS

CATIONS: only one common, ammonium ion, NH4+

ANIONS: negatively charged ions containing two or more elements; the knowledge of the formula and charge of the most common are basic to naming compounds and writing formulas.

One of the elements usually involved is oxygen; theion names end in “ate” or “ite” as follows...

Key Polyatomic Anion Formers:Know these!

Br, I same as Cl

4A 5A 6A 7A12 C N O F3 P S Cl45

Permanganate (7B)like Perchlorate

Chromate (6B) like Sulfate

Polyatomic Anions of C, 4A

Most common: CO32- carbonate

HCO31- hydrogen carbonate,

“bicarbonate”

Others: CH3CO2- acetate (“C2H3O2

-”) CN- cyanide

Polyatomic Anions of N, P 5A

Nitrogen: NO3- nitrate

NO2- nitrite

(Remember also: NH4+, ammonium; N3-, nitride)

Phosphorus: PO43- phosphate

HPO42- hydrogen phosphate

H2PO41- dihydrogen phosphate

(Remember also: P3-, phosphide)

GROUP WORK

• CATION, ANION

• Cr3+ CO32-

• Ni2+ CN-

• Zn2+ NO2-

• Bi3+ H2PO4-

• Pb2+ N3-

• FORMULA, NAME

Polyatomic Anions of O, S (6A) Cr (6B)

Oxygen: OH- hydroxide

Remember also: O2- oxide

Sulfur: SO42- sulfate

SO32- sulfite

HSO4 - hydrogen sulfate

HSO3 - hydrogen sulfite

Remember also: S2-, sulfide Chromium: CrO4

2- chromate

The “hydroxides” and “oxides” of the metallic elements are referred to as “bases”; all other ionic combinations are referred to as “salts”

“BASES” and “SALTS”

Bases:

Mg(OH)2

NaOH

CaO

Fe(OH)3

Salts:

MgCl2 MgHSO4 MgCO3

Na3PO4 NaNO2 Na2SO3

Ca(NO3)2 Ca3N2 CaSO4

Fe(CN)2 Fe(CH3CO2)3 Fe(H2PO4)2

Polyatomic Anions of Cl, Br, I (7A) Mn (7B)

Fluorine, F forms only the monatomic anion F-; Bromine, Br and Iodine, I form the same ions as chlorine, Cl:

Chlorine: ClO- hypochlorite ClO2

- chlorite ClO3

- chlorate ClO4

- perchlorate

Remember also: Cl-, Chloride

Manganese: MnO4- permanganate

SUMMARY, NAMING IONIC SALTS AND BASES

State name of the cation, then name of the anion.

Cations with a variable charge are named by adding a Roman numeral

Monoatomic anions are named by changing

theirelemental name to end in “ide”

Polyatomic anions (memorized) end in “ite” or “ate”...

GROUP WORK

FORMULA

LiClO

Cd(BrO2)2

Co(IO3)3

KMnO4

Ag2CrO4

NAME

Solutions

• FORMULA• LiClO

• Cd(BrO2)2

• Co(IO3)3

• KMnO4

• Ag2CrO4

• NAME• lithium hypochlorite• cadmium bromite• cobalt(III) iodate• potassium

permanganate• silver chromate

Naming Binary Molecular Compounds

All compounds beginning with a metal or ammonium are named as “ ionic compounds.”

Compounds containing only two elements (“binary”) in which both elements in the formula are a non-metal or metalloid are named in a different manner...

The change in nomenclature reflects the fact that these compounds are “molecular” and not “ionic” in nature!

• Name the first element in the formula

• Name the second element in the formula to end in “ide”:

carbide, nitride, phosphide, oxide, sulfide, fluoride, bromide, chloride, iodide •Add numerical prefixes to indicate more than one atom of the element in the formula:

di (2), tri (3), tetra (4), penta (5), hexa (6), hepta (7), octa(8)

Binary Molecular Nomenclature Method:

Typical Nomenclature

• NO2

• SF6

• ICl5

• N2O5

• CBr4

• SO3

• P2O3

• nitrogen dioxide• sulfur hexafluoride• iodine pentachloride• dinitrogen pentoxide• carbon tetrabromide• sulfur trioxide• diphosphorus trioxide

• BH3

• CH4

• SiH4

• NH3

• PH3

• borane

• methane*

• silane

• ammonia*

• phosphine

COMMON NAMES, BINARY MOLECULES ENDING IN H