Chapter 7 Part 2 Chemical Nomenclature CHM 1010 PGCC Barbara Gage “Chemical Nomenclature as we know it is born with the publication of Méthode de nomenclature

Chapter 7 Part 2Chemical Nomenclature

CHM 1010 PGCC Barbara Gage

“Chemical Nomenclature as we know it is born with the publication of Méthode de nomenclature chimique by Antoine-Laurent Lavoisier, Claude-Louis Berthellot, Antoine de Fourcroy, and Guyton de Morveau. The names proposed were based on the elements origin or function. (Image produced courtesy of the Library & Information Centre, Royal Society of Chemistry)”

http://www.rsc.org/chemsoc/timeline//pages/1787.html

System of rules for naming pure substances Elements – element name used even if the

substance is di- or polyatomicO2 = oxygen S8 = sulfur

Compounds - naming differs depending on whether a substance is held together primarily by ionic or covalent bonds.


Chemical Nomenclature


--

--1+

2+ 3+ 1-2-3-Generally metals form cations and non-metals form anions.

Cations (positively charged ions) and anions (negatively charged ions) will associate with each other and form a neutral binary compound to reduce energy .

1 Na+ 1 Cl- NaCl 1 Ca2+ 1 O2- CaO 3 K+ 1 N3- K3N 2 Al3+ 3 S2- Al2S3


Binary Ionic Compounds

Naming binary ionic compounds

The name of the cation is the same as the name of the metal.

Many metal names end in -ium.

The name of the anion (negatively charged ion) takes the root of the nonmetal name and adds the suffix -ide.

Calcium and oxygen form calcium oxide.

Aluminum and sulfur form aluminum sulfide.

The name of the cation (positively charged ion) is written first, followed by that of the anion.



Naming Ionic Binary Compounds

Naming Binary Ionic Compounds

PROBLEM: Name the ionic compound formed from the following pairs of elements:

PLAN:

(a) magnesium and nitrogen

SOLUTION:

Use the periodic table to decide which element is the metal and which the nonmetal. The metal (cation) is named first and we use the -ide suffix on the nonmetal name root.

(b) iodine and cadmium(c) strontium and fluorine (d) sulfur and potassium

(a) magnesium nitride(b) cadmium iodide

(c) strontium fluoride(d) potassium sulfide

From Silberberg, Principles of ChemistryCHM 1010 PGCC Barbara Gage

Determining Formulas of Binary Ionic Compounds

PROBLEM: Write simplest formulas for the compounds named in Sample Problem 2.5.

PLAN:

SOLUTION:

Compounds are neutral. We find the smallest number of each ion which will produce a neutral formula. Place subscripts to the right of the element symbol.

(a) Mg2+ and N3-; three Mg2+(6+) and two N3-(6-); Mg3N2

(b) Cd2+ and I-; one Cd2+(2+) and two I-(2-); CdI2

(c) Sr2+ and F-; one Sr2+(2+) and two F-(2-); SrF2

(d) K+ and S2-; two K+(2+) and one S2- (2-); K2S


The “B” group elements may form cations with more than one charge.

To specify which cation forms a compound, a roman numeral equal to the charge is added to the cation name.Fe2+ = iron (II) Fe3+ = iron (III)


Binary Ionic Compounds



Sample Problem 2.7 Determining Names and Formulas of Ionic Compounds of Elements That Form More Than One Ion

PLAN:

SOLUTION:

Compounds are neutral. We find the smallest number of each ion which will produce a neutral formula. Use subscripts to the right of the element symbol.

PROBLEM: Give the systematic names for the formulas or the formulas for the names of the following compounds:

(a) tin(II) fluoride (b) CrI3(c) manganese (IV) sulfide (d) CrO3

(a) Tin (II) is Sn2+; fluoride is F-; so the formula is SnF2.(b) The anion I is iodide(I-); 3I- means that Cr(chromium) is +3. CrI3 is chromium(III) iodide(c) Manganese (IV) is Mn2+; oxide is S2-, therefore the formula is MnS2.(d) Cr is chromium; the anion O is oxide(2-); the compound is cobalt (VI) oxide.

Modified from Silberberg, Principles of Chemistry

Some atoms form bonds that hold atoms together in a structure that has an overall charge (rather than as a neutral compound. These ions are called polyatomic ions.

CO32- carbonate SO4

2- sulfate Compounds with polyatomic ions are named with

the cation and anion name. Na2SO4 – sodium sulfate


Polyatomic Ions



Determining Names and Formulas of Ionic Compounds Containing Polyatomic Ions

PLAN:

SOLUTION:

Note that polyatomic ions have an overall charge so when writing a formula with more than one polyatomic unit, place the ion in a set of parentheses.

PROBLEM: Give the systematic names or the formula or the formulas for the names of the following compounds:

(a) Fe(ClO4)2 (b) sodium sulfite

(a) ClO4- is perchlorate; iron must have a 2+ charge.

This is iron(II) perchlorate.(b) The anion sulfite is SO3

2- therefore you need 2 sodiums per sulfite. The formula is Na2SO3.

Some compounds have water molecules attached as part of their structure. These are termed hydrates.

CuSO4. 5H2O

copper (II) sulfate pentahydrate


Hydrates

Numerical Prefixes for Hydrates and Binary Covalent CompoundsNumber Prefix Number Prefix Number Prefix

1 mono2 di3 tri

4 tetra5 penta6 hexa

8 octa9 nona10 deca

When certain binary gases dissolve in water they form acids with the same formula. The name is changed to add –ic acid to the anion

HCl (g) HCl (aq)hydrogen chloride hydrochloric acid


Binary Acids

HF (aq) hydrofluoric acid HCl (aq) hydrochloric acid HBr (aq) hydrobromic acid HI (aq) hydroiodic acid HCN (aq) hydrocyanic acid


Binary Acids

Acids containing oxygen; most do not exist in the same form without water

HNO3 nitric acidHNO2 nitrous acidH2SO4 sulfuric acidH2CO3 carbonic acidH3PO4 phosphoric acidHC2H3O2 or CH3COOH acetic acid


Oxyacids

Non-metals form bonds by sharing electrons rather than transferring them.

The resulting bond is referred to as a covalent bond.

The element farthest to the left or lower on the periodic table is generally written first. Subscripts are replaced by numerical prefixes in the name.


Covalent Binary Compounds


Covalent Binary Compounds


Naming Binary Covalent Compounds


Determining Names and Formulas of Binary Covalent Compounds

SOLUTION:

PROBLEM: (a) What is the formula of carbon disulfide?

(b) What is the name of PCl5?

(a) Carbon is C, sulfide is sulfur S and di-means 2 - CS2.

(b) P is phosphorus, Cl is chloride, the prefix for 5 is penta-. Phosphorus pentachloride.


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Chapter 7 Part 2 Chemical Nomenclature CHM 1010 PGCC Barbara Gage “Chemical Nomenclature as we know it is born with the publication of Méthode de nomenclature