CRISS -CROSS METHOD
1. The symbols of the component radicals of the compound are written side by side.
2. Positive radicals are written left and negative radicals on the right.
3. The valencies of the radicals are written above the respective symbols.
4. The criss-cross method is applied to exchange the numerical value of valency of each radical and it is written as subscript of the other radical.
5. The radical is enclosed in a bracket and the subscript is placed outside the lower right corner.
6. The common factor is removed.
7. If the subscript of the radical is one, it is omitted.
SOME IMPORTANT RADICALS
Monovalent
|
Bivalent
| ||
Positive
radicals |
Negative
radicals |
Positive
radicals |
Negative
radicals |
Lithium,Li+
|
Fluoride,F-
|
Beryllium,Be2+
|
Oxide,O2-
|
Sodium,Na+
|
Chloride,Cl-
|
Magnesium,Mg2+
|
Sulphide,S2-
|
Potassium,K+
|
Bromide,Br-
|
Calcium,Ca2+
|
Chromate,CrO42-
|
Rubidium,Rb+
|
Iodide,I-
|
Strontium,Sr2+
|
Dichromate,Cr2O72-
|
Caesium,Cs+
|
Hydroxide,OH-
|
Barium,Ba2+
|
Tetraborate,B4O72-
|
Ammonium,NH4+
|
Cyanide,CN-
|
Ferrous (Iron),Fe2+
|
Silicate,SiO32-
|
Silver,Ag+
|
Nitrate,NO3-
|
Zinc,Zn2+
|
Hydrogen Phosphate,HPO42-
|
Cuprous (copper),Cu+
|
Nitrite,NO-2
|
Cupric (copper),Cu2+
| |
Acetate,CH3COO-
|
Mercuric,Hg2+
|
Oxalate,C2O42-
| |
Hydrogen,H+
|
Hydride,H-
|
Manganous,Mn2+
| |
Bicarbonate,HCO3-
|
Chromous,Cr2+
|
Carbonate,CO32-
| |
Aurous (Gold),Au+
|
Bisulphate,HSO4-
|
Stannous (Tin),Sn2+
|
Sulphate,SO42-
|
Bisulphite,HSO3-
|
Plumbous (Lead),Pb2+
|
Sulphite,SO2-3
| |
Chlorate,ClO3-
|
Cobaltous,Co2+
|
Thiosulphate,S2O32-
| |
Hypochlorate,ClO-
|
Nickel(ous),Ni2+
| ||
Permanganate,MnO4-
|
Cadmium,Cd2+
|
Manganate,MnO42-
| |
Perchlorate,ClO4-
|
Thionyl,SO2+
| ||
Metaborate,BO2-
|
Platinous(Platinum),Pt2+
| ||
Amide,NH-2
| |||
Ethoxide,C2H5O-
| |||
Cyanate,CNO-
| |||
Thiocyanate,CNS-
| |||
Isothiocyanate,NCS-
| |||
Azide,N3-
| |||
Trivalent
|
Tetravalent
| ||
Positive
radicals
|
Negative
radicals
|
Positive
radicals
|
Negative
radicals
|
Boron,B3+
|
Carbon,C4+
|
Carbide,C4 -
| |
Nitogen,N3+
|
Nitride,N3-
|
Silicon,Si4+
|
Pyrophosphate,
P2O74-
|
Phosphorous,P3+
|
Phosphide,P3-
|
Platinic(Platinum),
Pt4+
| |
Aluminium,Al3+
|
Titanium,Ti4+
| ||
Bismuth,Bi3+
|
Orthoborate,BO33-
|
Ceric,Ce4+
| |
Ferric (Iron),Fe3+
|
Ferricyanide,
[Fe(CN)6]3-
|
Stannic(Tin),Sn4+
|
Ferrocyanide,
[Fe(CN)6]4-
|
Manganic,Mn3+
|
(Ortho)phosphate,
PO43-
|
Plumbic(Lead),Pb4+
| |
Chromium(ic),Cr3+
|
Phosphite,PO33-
| ||
Auric(Gold),Au3+
| |||
Cobaltic,Co3+
| |||
Exercise
| |||||||
Negative
Radicals
|
Chloride
|
Nitrate
|
Sulphate
|
Carbonate
|
Hydroxide
|
Oxide
|
Sulphide
|
Positive
Radicals
|
Cl-
|
NO3-
|
SO42-
|
CO32-
|
OH-
|
O2-
|
S2-
|
Hydrogen
H+
|
HCl
| ||||||
Sodium
Na+
|
NaNO3
| ||||||
Potassium
K+
|
K2SO4
| ||||||
Ammonium
NH4+
|
(NH4)2CO3
| ||||||
Magnesium
Mg2+
|
Mg(OH)2
| ||||||
Calcium
Ca2+
|
CaO
| ||||||
Zinc
Zn2+
|
ZnS
| ||||||
Aluminium
Al3+
|
AlCl3
| ||||||
Ferrous
Fe2+
| |||||||
Ferric
Fe3+
| |||||||
Cuprous
Cu+
|
CuCl
| ||||||
Cupric
Cu2+
|
Cu(NO3)2
| ||||||
Plumbous
Pb2+
| |||||||
Plumbic
Pb4+
| |||||||
Stannous
Sn2+
| |||||||
Stannic
Sn4+
| |||||||
Chromous
Cr2+
|
CrSO4
| ||||||
Chromic
Cr3+
|
Cr2(SO4)3
| ||||||
Mercurous
Hg22+
|
Hg2Cl2
| ||||||
Mercuric
Hg2+
|
HgCl2
| ||||||
Manganous
Mn2+
|
Mn(OH)2
| ||||||
Manganic
Mn3+
| |||||||
Silver
Ag+
|
AgNO3
| ||||||
Nickelous
Ni2+
|
NiCl2
|
NiS
| |||||
Barium
Ba2+
|
BaSO4
| ||||||
Cobaltous
Co2+
|
Co(NO3)2
| ||||||
Cobaltic
Co3+
| |||||||
Aurous
Au+
| |||||||
Auric
Au3+
|
AuCl3
| ||||||
Platinic
Pt4+
|
PtCl4
| ||||||
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