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NOMENCLATURE OF CHEMICAL COMPOUNDS

Chemistry

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

CO32-                 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

MgCO                   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

HNO                            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 CuCO

 

See also

PARTICULATE NATURE OF MATTER

STANDARD SEPARATION TECHNIQUES

COMPOUNDS AND MIXTURES

ELEMENTS

NATURE OF MATTER

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