NOMENCLATURE OF CHEMICAL COMPOUNDS

NAMING OF BINARY COMPOUNDS

Nomenclature: This is the system of naming chemical compounds. The system is called IUPAC (International union of pure and applied chemistry). The naming is determined by the constituent elements in the compound and the oxidation number if necessary.

In naming binary compounds (compounds with only two elements), electropositive elements (cations) are usually named first while the electronegative elements (anions) come last with a modification of the name end with – ide.

Examples:

Formula               IUPAC name

MgO                  Magnesium oxide

H₂S                    Hydrogen sulphide

NH₄Cl                Ammonium chloride

NaH                   Sodium hydride

But in cases where the two elements involved are non-metals, the above rule is not followed. For example, H₂O (water) NH₃ (ammonia) and PH₃ (phosphine)

 

EVALUATION

Name the following compounds: (a) NaCl (b) CaO (c) H₂O₂.

 

NAMING OF RADICALS AND COMPOUNDS HAVING ELEMENTS WITH VARIABLE OXIDATION NUMERS

Radicals (group of atoms of element carrying electrical charge) are treated as a single element when naming their compounds.

Examples of radicals with their names are as follows:

Radical                    IUPAC NAME

NH4⁺                       Ammonium ion

OH^‑                                        Hydroxyl ion

But in naming acid radicals, the oxidation number of elements is indicated by Roman numbers in bracket.

Example:

Formula             IUPAC

NO₂‑                  Dioxonitratei(iii) ion

NO₃^–                   Trioxonitrate(v) ion

CO₃^2-                 Trioxocarbonate(iv) ion.

Also the compounds having elements with Roman numbers in bracket indicating their oxidation numbers in that compound

Examples

Formula                   IUPAC

FeO                          Iron (ii) oxide

Cu₂O                        Copper (i) oxide

MgCO₃                     Magnesium trioxocarbonate (iv)

 

EVALUATION

1. Name the following compounds (a) Fe₂O₃  (b) CuO
2. What are the oxidation numbers of Fe and Cu in (1) above?

 

NAMING TERTIARY COMPOUNDS AND QUARTENARY COMPOUNDS.

These are compounds containing more than two elements.

Examples are oxo-acids, normal salts, and acid salts.

Acid                                 IUPAC

HNO₃                              Trioxonitrate(v) acid

H₂SO₄                             Tetraoxosulphate (vi) acid

H₃PO₄                             Tetraoxophospate (v) acid

      Examples of Normal Salts.

Normal salts                      IUPAC

KNO₃                               Potassium trioxonitrate (iv)

NaSO₄                             Sodiumtetraoxosulphate (vi)

CuCO₃                              Copper (ii) trioxocarbonate (iv)

 

EVALUATION 

1. Determine the oxidation number of: a) C in H₂CO₃ b) Mn in KMnO₄ c) Cu in CuSO₄
2. Name the compounds in 1 above

 

NAMING OF COMPOUNDS WHOSE CATIONS HAS BEEN PARTIALLY REPLACED WITH HYDROGEN IONS.

In naming compounds whose cations have been partially replaced with hydrogen ion, the cations is named first followed by hydrogen, then the radicals present indicating the roman number standing for the oxidation number of the element that is combined with oxygen to form the radical.

E.g Formula                                IUPAC

NaHSO₄                                       Sodium hydrogen tetraoxosulphate (vi)

KHSO₃                                        Potassium hydrogen trioxosulphate (iv)

 

GENERAL EVALUATION/REVISION

1. Determine the following oxidation number of a) C in LiHCO₃ b) S in KHSO₄ and name the compounds
2. Write the chemical formula of the following compounds a) Oxochlorate (I) acid b) Iron (ii) tetraoxosulphate (VI) pentahydrate
3. State the uses of the following laboratory apparatuses a) Condenser b) Kipp’s apparatus c)Tripod stand.

 

WEEKEND ASSIGNMENT

1. The compound Na₂S is called ____ (a) Sodium (ii) sulphate (b) Sodium sulphur (c) Sodium sulphide (d) Sodium sulphite.
2. The formula of sulphur (iv) oxide is (a) SO₄ (b) SO₂ (c) S₂O₄ (d) S₄O₂
3. Ammonium chloride can be written as (a) NH₄Cl (b) NH₃Cl₂ (c) NH₄HCl (d) NH₄OH

1. The IUPAC name of NaHSO₄ is (a) Sodium bicarbonate (b) Sodium tetraoxosulphate (vi) acid (c) Sodium sulphate (c) Sodium hydrogen tetraoxosulphate (vi)
2. Which of the following compounds have cation with variable oxidation state. (a) FeO₃ (b) ZnCO₃   (c) CuO (d) KU

 

THEORY

1. Name the following compounds (a) Fe₂O₃ (b) KMnO₄ (c) KClO₃
2. Calculate the oxidation number of (a) Sulphur in H₂SO₄ (b) Carbon in CuCO₃ 

 

See also

PARTICULATE NATURE OF MATTER

STANDARD SEPARATION TECHNIQUES

COMPOUNDS AND MIXTURES

ELEMENTS

NATURE OF MATTER