write the valence of different groups
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order to write chemical formulae we need to understand how elements combine with each other to form molecules or ionic compounds. Ionic compounds are substances made from the combination of charged ( positive and negative) particles.
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Classification of Elements and Periodicity in Properties
Periodicity Of Valence Or Oxidation States Of Elements

Valency Chart (Valency Table of Chemical Elements)
What does the term ‘Valency’ mean?
The valency of an element is a measure of its combining capacity and can be defined as
the number of electrons that must be lost or gained by an atom to obtain a stable electron configuration.
What does the term ‘Oxidation State’ mean?
The oxidation state of an atom is the number of electrons lost or gained by it.
Oxidation State and valency are one of the most fundamental properties of elements and can be studied with the help of electron configurations.
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Tetravalency of Carbon
Concept of Valency
Valency and Oxidation State
Electrons that are found in the outermost shell are generally known as valence electrons and the number of valence electrons determines the valency (or valence) of an atom.
The valencies of the elements belonging to the s-block and the p-block of the periodic table are generally calculated as the number of valence electron or eight minus the number of valence electrons.
For the d-block and f-block elements, valency is determined not only on the basis of valence electrons but also on d and f orbital electrons. However, the general valencies of these d and f block elements are 2 and 3.
The general oxidation state of the elements of the periodic table is illustrated in the chart provided below.

Oxidation State and Valency Chart
Valency of First 30 Elements
The valency of the first 30 elements of the periodic table is given below.
ElementAtomic NumberValencyValency of Hydrogen11Valency of Helium20Valency of Lithium31Valency of Beryllium42Valency of Boron53Valency of Carbon64Valency of Nitrogen73Valency of Oxygen82Valency of Fluorine91Valency of Neon100Valency of Sodium (Na)111Valency of Magnesium (Mg)122Valency of Aluminium133Valency of Silicon144Valency of Phosphorus153Valency of Sulphur162Valency of Chlorine171Valency of Argon180Valency of Potassium (K)191Valency of Calcium202Valency of Scandium213Valency of Titanium224Valency of Vanadium235,4Valency of Chromium242Valency of Manganese257, 4, 2Valency of Iron (Fe)262, 3Valency of Cobalt273, 2Valency of Nickel282Valency of Copper (Cu)292, 1Valency of Zinc302