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	Symbols	Valencies	Names of acidic radicals	Symbols	Valencies
Aluminium	Al3+	3	Sulphite		2
Ammonium		1	Bromide	Br−	1
Calcium	Ca2+	2	Carbonate		2
Copper(II)	Cu2+	2	Chloride	Cl−	1
Hydrogen	H+	1	Hydride	H−	1

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