CHEMICAL NOMENCLATURE

What’s in the name?Chemical nomenclature is the

term given to the naming of compounds. It is used to identify a chemical species by means of written or spoken words. It is a useful means for communication among chemists. The name of the compound contains within itself an implied relationship to the structure of the compound.

Lesson 1. Chemical Symbol

There are 114 known elements at present.

Among the 114 elements, 11 are known to be gases. Some of these are oxygen,

hydrogen, nitrogen, chlorine, and helium. Elements

like neon, argon, krypton,xenon,radon, and fluorine are very rare and are not found in large

quantities in nature. All the rest are solids.

Before the year 1814, the chemical symbols were expressed this way:

Element Symbol

Iron ♂

Copper ♀

Gold Ο

Then Jon Jacob Berzelius (1779-1848), a Swedish chemist, started to use chemical symbols. He used the initial letter of the element’s Latin or common name in its capitalized form as its chemical symbols as follows:

C = carbon O = oxygen I = iodine

This practice is still followed today. If the two elements start with the same letter, two letters are used as in the following:

Ca = calciumCo = cobalt

What do you think is the symbol for each of the following elements?

a. hydrogenb. heliumc. borond. barium

1. What is the correct symbol for cuprum?

a. C c. Cp

b. Cu d. Cr

2. Which of the following does NOT belong to the group?

a. Argentum c. Calcium

b. Aurum d. Kalium

3. Which of the following elements is a solid?

a. argon c. helium

b. carbon d. hydrogen

4. What is the English name of stibium?

a. Antimony c. lead

b. arsenic d. tin

5. Which of the following does NOT belong to the group?

A. carbon c. nitrogen

B. hydrogen d. oxygen

Lesson 2. Chemical Formula Chemical Formulas:

Chemical formulas such as MgSO4 can be divided into empirical formula, molecular formula, and structural formula. The chemical symbols of elements in the chemical formula represent the elements present in the compound. The subscript numbers represent mole proportions of the preceding elements. If no number is written, it means the subscript is 1.

The Writing of Formulas

Binary Ionic Compound (compound composed of metal and

a nonmetal) The metal acts the cation (positively-

charged ion) while the nonmetal forms the anion (negatively-charged ion). The first part of the name of an inorganic compound is the first part of the formula.

Formula Writing of Binary Ionic compounds

Charge – Crossing Technique

Activity

1. hydrogen chloride (you must know that this is the common muriatic acid for cleaning purposes)

2. calcium fluoride (do you still remember the anti tartar ingredient of your toothpaste?)

3. sodium oxide (the substance behind the cleansing principle of your laundry detergent)

1. HCl

2. CaF2

3. Na2O

The Naming of

Compounds: Nomenclature

Identifying a Compound as Ionic or Molecular

Metals combined with nonmetals will

produce compounds that are ionic.

Nonmetals combined with nonmetals will produce compounds that are molecular.

Nomenclature of Binary Ionic Compounds

A binary compound is

made up of two different elements.

Points to remember about naming a compound from its

formula1. The order for names in a binary compound is first the cation, then the anion.

2. Use the name of cation directly from the periodic table.3. The name of the anion will be made from the root of the element's name plus the suffix "-ide."

Example: Write the name of this formula: H2S

QUIZ:

Nomenclature of Acids and Bases

For the purposes of naming acids and bases, we will classify these chemicals

into three categories: binary acids, ternary

acids (sometimes called oxy-acids), and bases.

Binary Acids

Binary acids contain hydrogen and one other

nonmetallic element. Their names follow the pattern of

"hydroelementic acid" where element is

replaced by the root of the name of the element.

These acids contain no oxygen. Here are some

examples.

Binary acids

Binary Acids HF (aq)

hydrofluoric acid HCl (aq) hydrochloric

acid HBr (aq) hydrobromic

acid HI (aq) hydroiodic

acid HCN (aq) hydrocyanic

acidCHM 1010 PGCC Barbara Gage

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 acid

CHM 1010 PGCC Barbara Gage

Bases Bases are simply named as ionic compounds containing the hydroxide

ion. Here are some examples.

Empirical (Simplest) formula is a formula whose subscripts

represent the simplest whole number ratio of atoms in a molecule

or the simplest whole number ratio of moles of each element in a mole of

the compound. The simplest formula is usually determined by considering experimental data, hence the name "empirical" which means based on

experimentation.

Lesson 3. Empirical and Molecular Formula

Molecular formula gives the exact number of atoms of

each element per molecule of the compound or the absolute

number of moles of each element per mole of the compound. A

molecular formula may be reducible to a simple formula if

all its subscripts are divisible by a common denominator.

To determine the molecular formula of the compound, just follow these steps:

1. Find the mass of the empirical unit.

2. Figure out how many empirical units are in a molecular unit.

3. Write the molecular formula.

Example:

A compound with an empirical formula of

CH has a molar mass of 78. What is

its molecular formula?

Answer:

Step #1. C : 12 x 1 = 12 H : 1 x 1 =

1_ 13

Step #2. 78/13 = 6Step #3. (CH)6 = C6H6

On the other hand, if the empirical formula is

asked, simply divide the subscripts of the

molecular formula with the greatest common factor. The resulting

SIMPLEST WHOLE NUMBER represents the

subscript in the empirical formula.

Example: What is the empirical formula of the compound Na2C2O4?

Answer: Just divide the subscripts of the molecular formula by the greatest common factor.

The resulting empirical formula is

NaCO2.

molecular mass C12H22O11 = 12(mass of C) + 22(mass of H) + 11(mass of O)molecular mass C12H22O11 = 12(12.01) + 22(1.008) + 11(16.00)molecular mass C12H22O11 = = 342.30