PLEASE GIVE ME THE LIST OF BOTH BASIC AND ACIDIC RADICALS WITH THEIR SIGNS..                                          AND TELL HOW TO MAKE FORMULAS ..

Here are tables, in which the commonly used acidic and basic radicals are listed. Hope this will help you.

Name of basic radicals

SymbolsValenciesNames of acidic radicalsSymbolsValencies
AluminiumAl3+3Sulphite2
Ammonium1BromideBr1
CalciumCa2+2Carbonate2
Copper(II)Cu2+2ChlorideCl1
HydrogenH+1HydrideH1

Names of basic radicals

Symbols

Valencies

Names of acidic radicals

Symbols

Valencies

Iron(II)

Fe2+

2

Hydrogen

carbonate

1

Iron(III)

Fe3+

3

Hydroxide

OH

1

Magnesium

Mg2+

2

Nitrate

1

Nickel

Ni2+

2

Nitrite

1

Potassium

K+

1

Oxide

O2−

2

Silver

Ag+

1

Phosphate

3

Sodium

Na+

1

Sulphate

2

Zinc

Zn2+

2

Sulphide

S2−

2

And, following rules need to be kept in mind while writing the chemical formulae of compounds.

The valencies or charges on the ions must be balanced. The charge on a cation must be equal in magnitude to the charge on an anion so that the opposite charges cancel each other out and the net charge of the molecule becomes zero.

Examples

  • In case of CaO, the valency of Ca is +2 and that of O is −2. These are then crossed over and the compound formed is CaO.

Formula of calcium oxide

Symbols Ca O

Charges 2+ 2−

  • The charge on Mg2+ is +2 and that on Cl is −1. Thus, one Mg2+ ion combines with two Cl ions to form a molecule with the formula MgCl2.
  • In case of a compound consisting of a metal and a non-metal, the symbol of the metal is written first.

Example

  • In calcium chloride (CaCl2) and zinc sulphide (ZnS), calcium and zinc are metals, so they are written first; chlorine and sulphur are non-metals, so they are written after the metals.
  • In case of compounds consisting of polyatomic ions, the polyatomic ions are enclosed in brackets before writing the number to indicate the ratio.

Example

  • In case of aluminium sulphate, to balance the charges, two ions combine with one Al3+ ion. Thus the formula for aluminium sulphate is Al2(SO4)3. Here, the brackets with the subscript 3 indicate that three sulphate ions are joined to two aluminium ions.

Formula of aluminium sulphate

Symbols Al SO4

Charges 3+ 2−

Example 2:

The valencies of a few ions are provided below.

H+ = 1, = 2, Br = 1, Mg2+ = 2 and K+ = 1

Write the formulae for magnesium bromide, magnesium sulphate, hydrogen bromide and potassium sulphate.

Solution:

Magnesium bromide: MgBr2

Magnesium sulphate: MgSO4

Hydrogen bromide: HBr

Potassium sulphate: K2SO4

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