Tuesday, 10 July 2012

How to learn naming Chemical Formulae?

Chemicals
(src:deviantart)
Nomenclature of Simple Inorganic compounds.


1. A formula is a shorthand notation used to identify the composition of a molecule or compound.

2. For example chemical formula of water is H2O. It includes the symbol of each element (e.g. Hydrogen:H and Oxygen:O)  in the molecule, along with numerical subscripts to show how many atoms of each element are present.

3. Most of the inorganic compounds are binary compounds i.e. it consists of two elements. Some are ternary i.e. contain more than two elements.


4. Compounds may be ionic compounds i.e. elements have ionic bonds. Or these can be covalent bonded. Generally, metal element forms ionic bond with non-metal element. Compounds having non-metals only have covalent bonding.

5. An atom or group of atoms with either a positive or a negative charge is called an Ion

6. Cations are positively charged ions.

7. Anions are negatively charged ions (Are Negative IONS)

8. Monatomic Ion means a single atom ion (mono = one) Ex: Na+ or Cl-

9. Polyatomic Ion means a group of atom ions (poly means many) which acts together as single unit. For example: Nitrate polyatomic ion NO3- (1 Nitrogen atom, 3 Oxygen atoms has one extra electron and thus is negatively charged 1-).

10. For binary compounds containing  a metal and a non-metal, metal is always named first, followed by a name derived from the root name for the nonmetal. E.g. Common Salt NaCl consists metal (cation: Na+) and non-metal Chlorine becomes chloride here (anion: Cl-)

11. Usually anions of an element carrying one negative charge (1-) have suffix -ide

Element Anion                  Name used in formula   
Cl-Chloride
F-Fluoride
Br-Bromide
I-Iodide
O2-Oxide
S2-Sulphide
H-Hydride
Au-Auride
N3-Nitride
P3-Phosphide
As3-Arsenide

12.  The net charge on an ionic compound is always zero. E.g. In NaCl, one cation(Na1+) and one anion(Cl1-), makes the net charge (1+ + 1- = 0) zero. Similarly, in AlCl3. one cation (Al3+ ) and three anions (Cl1-), makes the net charge(3+ + 3(1-)= 0) zero.

13. Anions carrying oxygen+another element are called -oxy anions. In general, for -oxy anions we use suffix -ate is used. Few examples are:

  -oxy Anion                  Name used in formula   
CO32-Carbonate
SO42-Sulphate
SiO32-Silicate
ZnO32-Zincate

14. In case of -oxy anions, if non-metal element exists with oxygen in more than one charged (or oxidation) state, then we use suffix -ite for the lower charged state and -ate for higher charged state.

  -oxy Anion                  Name used in formula   
SO32-Sulphite
SO42-Sulphate
NO2-Nitrite
NO3-Nitrate
SnO22-Stannite
SnO32-Stannate

15. In case of -oxy anions, if more than two oxidation (charged) states exist, we use the following naming convention (Note: It is old traditional system, still in use. IUPAC time to time releases new nomenclature standards).

  Oxidation State              prefix- or -suffix
used in Anions   
LowestHypo-      -ite
.-ite
.-ate
.per-     -ate
HighestHyper-     -ate

An example of this:

  -oxy Anion                  Name used in formula   
ClO-Hypochlorite
ClO2-Chlorite
ClO3-Chlorate
ClO4-Perchlorate
HPO32-Phosphite
H2PO2-Hypophosphite

16. When an polyatomic anion has H- associated with it, we use bi- or hydrogen- as suffix root name.
For example,

  Polyatomic Anion  
with H-               		 Name used in formula   
HCO3-bicarbonate
or hydrogen carbonate   
HSO4-bisulphate or
hydrogen sulphate
HSO3-bisulphite or
hydrogen sulphite
HS-bisulphide or
hyderogen sulphide  
HPO42-monohydrogen phosphate
H2PO4-dihydrogen phosphate
(Note: to represent number of atoms, prefixes like mon-, bi-, di-, tri- etc. are used).

17. List of a few other polyatomic anions

  Polyatomic Anions                           Name used in formula                
OH-Hydroxide
O2-Superoxide
O3-Ozonide
NH2-Amide 
N3-Azide
CN-Cyanide
OCN-Cyanate
SCN-thiocynate
CrO22-Chromate
Cr2O72-DiChromate
MnO42-Manganate
MnO4-Permangnate
CH3COO-Acetate
C2O42-Oxalate
PO43-Phosphate

18. List of Cations whose charge do not vary

Single Charge                Double Charge                          Triple Charge
HydrogenH+BerylliumBe2+AluminiumAl3+
LithiumLi+MagnesiumMg2+

SodiumNa+CalciumCa2+

PotassiumK+StrontiumSr2+

CesiumCs+BariumBa2+

RubidiumRb+ZincZn2+

SilverAg+CadmiumCd2+

AmmoniumNH4+


19. Following is the list of cations whose charges vary. In traditional system, we use suffix -ous with lower charged state and -ic with higher charged state. The new IUPAC method, the charged state is represented with Roman numerals within parentheses. For example:

Element      Cation     IUAPC Name          Tradional Name    Example
CopperCu+Copper(I)Cuprous
CopperCu2+Copper(II)Cupric
GoldAu+Gold(I)AurousAuCl Gold(I) Choloride
or Aurous Chloride
GoldAu3+Gold(III)AuricAuCl3 Gold (III) Chloride
or Auric Chloride
IronFe2+Iron(II)Ferrous
IronFe3+Iron(III)Ferric
MercuryHg+Mercury(I)Mercurous
MercuryHg2+Mercury(II)Mercuric
ChromiumCr2+Chromium(II)

ChromiumCr3+Chromium(III)

ChromiumCr6+Chromium(VI)

CobaltCo2+Cobalt(II)

CobaltCo3+Cobalt(III)

ManganeseMn2+Manganese(II)

ManganeseMn3+Manganese(III)

ManganeseMn7+Manganese(VII)


20. In some cases cations containing non-metals, we use suffix -nium
For example:

   Cations                           Name used in formula                
NH4+Ammonium
NH2H5+Hydrazinium
C5H6N+pyridinium
H3O+Hydronium 
NO2+Nitronium

21. Acid is any substance that has one or more replaceable hydrogen ions (H+).

22. Acids which do not contain oxygen are named with prefix hydro-
A few examples are:

   Acid                Name                 
HFHydroflouro acid
HClHydrochloric acid
HBrHydrobromic acid
HIHydroiodic acid
HCNHydrocyanic acid
H2SHydrosulphuric acid or Hydrogen Sulphide
(Do not confuse with Sulphuric acid H2SO4)
HN3Hydrazoic acid

23. List of acids which contain oxygen.

   Acid                Name                 
H2CO3Carbonic acid
H3CO3Boric acid
H4SiO4Silicic acid
HNO3Nitric acid
HNO2Nitrous acid
H2SO4Sulphuric acid
H2SO3Sulphurous acid
H2S2O3Thiosulphuric acid
H2CrO4Chromic acid
H2Cr2O7Dichromic acid
H3PO4Phosphoric acid
H3PO3Phosphorous acid
H3AsO4Arsenic acid
H3AsO3Arsenious acid
HClO4Perchloric acid
HClO3Chloric acid
HClO2Chlorous acid
HClOHypochlorous acid
HMnO4Permanganic acid
HOCNCyanic acid
HSCNThiocyamc acid
CH3COOH Acetic acid
H2C2O4Oxalic acid

Q1: Write the chemical formula of the following. List the cations and anions present.
(a) sodium chloride
(b) potassium iodide
(c) calcium sulfide
(d) cesium bromide
(e) magnesium oxide

Answer: 
(a) sodium chloride:  NaCl (Na+, Cl-)
(b) potassium iodide: KI (K+, I-)
(c) calcium sulfide: CaS(Ca2+, S2-)
(d) cesium bromide: CsBr (Cs+, Br-)
(e) magnesium oxide: MgO (Mg2+, O2-)

Q2: Name the following binary compounds.
(a) AlCl3
(b) CsF
(c) MgI2
(d) CaCl2
(e) LiCl
(f) MgS
(g) Rb2O
(h) CaO

Answer: 
(a) AlCl3: Aluminium Chloride
(b) CsF  : Cesium Fluoride

(c) MgI2: Magnesium Iodide
(d) CaCl2: Calcium Chloride
(e) LiCl : Lithium Chloride
(f) MgS : Magnesium Oxide
(g) Rb2O : Rubidium oxide
(h) CaO: Calcium Oxide

Q3: Give chemical formula for the following compounds.
(a) iron (III) Chloride
(b) ferric oxide
(c) sodium hydroxide
(d) cobaltous hydroxide or cobalt(II) hydroxide
(e) tin (IV) Hydroxide
(f) mercuric cyanide

Answer:
(a) iron (III) Chloride:  FeCl3:
(b) ferric oxide: Fe2O3
(c) sodium hydroxide: NaOH
(d) cobaltous hydroxide or cobalt(II) hydroxide: Co(OH)2
(e) tin (IV) hydroxide: Sn(OH)4
(f) mercuric cyanide: Hg(CN)2

Q4: Give chemical formula for the following compounds:
  1. Potassium chlorite
  2. Magnesium sulphite
  3. Chromium sulphate
  4. Sodium acetate
  5. Lead chloride
  6. Cuprous iodide
  7. Copper(II) sulphide
  8. Ferric chlorite
  9. Mercuric chloride
  10. Barium peroxide
  11. Strontium silicate
  12. Cobalt (III) nitrate
  13. Lithium hydride
  14. Ammonium cyanate
  15. Strontium manganate
  16. Silver oxalate
  17. Calcium phosphide
  18. Radium phosphate
  19. Aluminium nitride
  20. Zinc nitrate
Answer(incomplete):
  1. Potassium chlorite : KClO2
  2. Magnesium sulphite: MgSO3
  3. Chromium (III) sulphate: Cr2(SO4)3
  4. Sodium acetate: CH3COONa
  5. Lead chloride: PbCl2
  6. Cuprous iodide: CuI
  7. Copper(II) sulphide: CuS
  8. Ferric chlorite: Fe(ClO2)3
  9. Mercuric chloride: Mercury(II) Chloride - HgCl2
  10. Barium peroxide: BaO2
  11. Strontium silicate
  12. Cobalt (III) nitrate
  13. Lithium hydride
  14. Ammonium cyanate
  15. Strontium manganate
  16. Silver oxalate
  17. Calcium phosphide
  18. Radium phosphate
  19. Aluminium nitride
  20. Zinc nitrate

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