Valency Chart (Valency Table Of Chemical Elements) - Byju's

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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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 electrons 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.

Valency of First 30 Elements

The valency of the first 30 elements of the periodic table is given below.

Element	Atomic Number	Valency
Valency of Hydrogen	1	1
Valency of Helium	2	0
Valency of Lithium	3	1
Valency of Beryllium	4	2
Valency of Boron	5	3
Valency of Carbon	6	4
Valency of Nitrogen	7	3
Valency of Oxygen	8	2
Valency of Fluorine	9	1
Valency of Neon	10	0
Valency of Sodium (Na)	11	1
Valency of Magnesium (Mg)	12	2
Valency of Aluminium	13	3
Valency of Silicon	14	4
Valency of Phosphorus	15	3
Valency of Sulphur	16	2
Valency of Chlorine	17	1
Valency of Argon	18	0
Valency of Potassium (K)	19	1
Valency of Calcium	20	2
Valency of Scandium	21	3
Valency of Titanium	22	4
Valency of Vanadium	23	5,4
Valency of Chromium	24	2
Valency of Manganese	25	7, 4, 2
Valency of Iron (Fe)	26	2, 3
Valency of Cobalt	27	3, 2
Valency of Nickel	28	2
Valency of Copper (Cu)	29	2, 1
Valency of Zinc	30	2

Periodic Trends in the Oxidation States of Elements

1. Variation Of Oxidation State Along a Period

While moving left to right across a period, the number of valence electrons of elements increases and varies between 1 to 8. But the valency of elements, when combined with H or O first, increases from 1 to 4 and then it reduces to zero. Consider two compounds containing oxygen Na2O and F2O. In F2O, the electronegativity of F is more than oxygen. Hence, each of F atom will attract one electron from oxygen i.e. F will show -1 oxidation state and O will show +2 oxidation state. Whereas, in the case of Na2O, oxygen is highly electronegative than sodium atom. So oxygen will attract one electrons from each sodium atom showing -2 oxidation state and Na will have +1 oxidation state. The oxidation state of the element represents the charge possessed by an atom due to the loss or gain of electrons (due to the electronegativity difference between the combining atoms) in the molecule.

2. Variation Of Oxidation State within a Group

As we move down in a group the number of valence electrons does not change. Hence, all the elements of a particular group group have the same valency.

Guidelines for assigning the Oxidation States

• Oxidation states of elements like O2, S8, H2, P4, Fe, etc are zero.
• Oxygen has an oxidation state of -2. But in its peroxides like Na2O2  and H2O2, it has -1 as its oxidation state
• Similarly, hydrogen has +1. But in Metal Hydrides, such as NaH, LiH, etc, it has -1
• Some elements have the same oxidation states as in their compounds such as
  1. Halogens have -1 except when they form a compound with one another or Oxygen.
  2. Alkali Metals such as Na, K, Rb, Li, Cs have +1
  3. Alkali Earth Metals have +2 such as Mg, Ca, Ba, Be, Sr, etc

Frequently Asked Questions – FAQs

Q1

What is a valency?

Valency is defined as the number of hydrogen atoms which combine directly or indirectly with one atom of an element. Example: One atom of nitrogen combines with three atoms of hydrogen to form ammonia gas. So, the valency of nitrogen is 3.

Q2

What is carbon valency?

The valency of carbon is four and one atom of carbon can make four covalent bonds.

Q3

What is Tetravalency?

Carbon has a valency of four, so it is capable of bonding with four other atoms of carbon or atoms of some other monovalent element. This is known as tetravalency of carbon.

Q4

Does valency have a charge?

Charge is the value that is attained when an atom loses or gains electrons; this also happens to satisfy the octet rule. Valency is defined for elements whereas charge is defined for loss. So, valency cannot be related to charge.

Q5

How do you write the valency of oxygen?

Atomic Number of oxygen is 8. electronic Configuration of oxygen= 2, 6. So the valency is 8-6 = 2.

To learn more about the periodicity in the properties of elements and the trends in the oxidation states of elements in the periodic table, download BYJU’S – The Learning App.