Chemical Nomenclature “Chemical Nomenclature as we know it is born with the publication of Méthode de nomenclature chimique by Antoine-Laurent Lavoisier,

Chemical Nomenclature

“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.htmlCHM 1010 PGCC Barbara Gage

Chemical Nomenclature

• 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.

CHM 1010 PGCC Barbara Gage

Ions…

• Electrons are arranged on levels or “shells”. Atoms are most stable with 8 electrons on their outermost shell. This is often referred to as the octet rule.

• Number of electrons on the outer shell = Group number for elements in Groups I-VIII A (using the US convention labeling on periodic table)


Figure 2.10The modern periodic table.The modern periodic table.

Silberberg, Principles of Chemistry

US Convention

IUPAC Convention


Ions…

• To achieve the octet, atoms with more than 4 electrons on the outer shell will gain enough electrons to reach 8.

• Cl Group 7 7 electrons on outer shell

Cl will gain 1 e- .• Now #e- = 18 but #p+ = 17 so the

chlorine is an ion with the formula Cl1-.


Ions…

• O Group 6 6 electrons on outer shell O will gain 2 e- .

• Now #e- = 10 but #p+ = 8 so the oxygen is an ion with the formula O2-.

• P Group 5 5 electrons on outer shell P will gain 3 e-

• Now #e- = 18 but #p+ = 15 so the phosphorus is an ion with the formula P3-


Ions…

• Na Group 1 1 electron on outer shell O will lose 1 e- to expose the complete inside shell.

• Now #e- = 10 but #p+ = 11 so the sodium is an ion with the formula Na1+.

• Mg Group 2 2 electrons on outer shell Mg will lose 2 e-

• Now #e- = 10 but #p+ = 12 so the magnesium is an ion with the formula Mg2+



--

--1+

2+ 3+ 1-2-3-

Generally metals form cations and non-metals form anions.

Binary Ionic Compounds

• 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


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


Binary Ionic Compounds

• 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)




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

Polyatomic Ions

• 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 sulfateCHM 1010 PGCC Barbara Gage



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 SO32- therefore you need 2

sodiums per sulfite. The formula is Na2SO3.

Hydrates• Some compounds have water

molecules attached as part of their structure. These are termed hydrates.

• CuSO4. 5H2O

copper (II) sulfate pentahydrate


Numerical Prefixes for Hydrates and Binary Covalent Compounds

Number Prefix Number Prefix Number Prefix

1 mono

2 di

3 tri

4 tetra

5 penta

6 hexa

8 octa

9 nona

10 deca

Binary Acids

• 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


Oxyacids

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

HNO3 nitric acid

HNO2 nitrous acid

H2SO4 sulfuric acid

H2CO3 carbonic acid

H3PO4 phosphoric acid

HC2H3O2 or CH3COOH acetic acidCHM 1010 PGCC Barbara Gage

Covalent Binary Compounds• 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



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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Chemical Nomenclature “Chemical Nomenclature as we know it is born with the publication of Méthode de nomenclature chimique by Antoine-Laurent Lavoisier,