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An Introduction to Valency Chart

Last updated date: 16th Mar 2023
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Valency can be defined as combining the power of an element or radical. The valency chart consists of the list of valencies of the element. We know the chemical formula of salt and water is NaCl and H2O respectively. But have you ever thought about what the reason for this specific formula is? How are these derived? The chemical formula of any element is written because of the valencies of its compound. In the following article we are going to discuss the answer to these questions which is ‘Valency’ , its examples and uses.


What does the term Valency mean? 

Valency is the combining capacity of an element. It is always a whole number. It has no plus or minus sign. The electrons present in the outermost shell of an atom are known as ‘Valence Electrons’. We can say valency is the number of electrons an element can lose or gain to attain stability. Valency is used to write the chemical formula of a compound. It means by valency we can know how the atoms of an element will combine with atoms of another element.


The Concept of Valency 

In atoms, electrons are arranged in a way that they revolve around the nucleus in different orbitals (shells). These orbitals are represented as K, L, M, N, and so on. The valence electron of atoms remains in the outermost shell of electrons. These outermost shell electrons take part in any chemical reaction as generally, they contain more energy than the electrons present in other orbits.


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According to the Octet rule, the outermost orbit of an atom will have a maximum of 8 electrons to become stable. However, if the outermost orbit is completely filled then sometimes very little to no chemical activity is observed in the particular element. 


Examples of valencies of elements

Some examples of elements are given below with the value of their valencies. Let’s understand the valency by following examples.

  1. Copper – Copper is a transition element. Most of the transition elements show variable valences. Copper shows two valences 1 and 2. If copper shows valency 1 or Cu(I) then it’s known as Cuprous while when it shows valency 2 or Cu(II) then it’s known as Cupric. 

  2. Nitrogen – Atomic number of nitrogen is 7. Its electronic configuration is 2, 5. So, it's clear that nitrogen has 5 electrons in its outermost shell. To complete its octet nitrogen needs 3 more electrons. By completing its octet, it will attain stability. Thus, the valency of nitrogen is 3. 

  3. Sodium – Atomic number of sodium is 11. Its electronic configuration is 2,8,1. So, it's clear that sodium needs to lose one electron to attain stability by completing its octet. Thus, its valency is 1. 

  4. Fluorine – Atomic number of fluorine is 9. Its electronic configuration is 2,7. It needs one electron to fulfil its octet and attain stability. So, its valency is 1. 

  5. Lithium – Atomic number of lithium is 3. Its electronic configuration is 2,1. So, it needs to lose one electron to attain stability and get an electronic configuration like noble gas Helium. Thus, its valency is 1. 

  6. Helium – Atomic number of helium is 2. Its outermost shell is already fulfilled. So, helium is a highly stable element and doesn't react with other elements easily. It is also known as inert gas or noble gas. Thus, the valency of helium is zero. 

  7. Nickel – Nickel is a transition element. So, it shows variable valences. Its atomic number is 28. It shows valences 2,3 and 4 majorly. 

  8. Phosphorus – Atomic number of phosphorus is 15. Its electronic configuration is 2,8,5. So, it needs 3 electrons to fulfill its outermost shell and attain stability. Thus, its valency is 3. 

  9. Scandium – Atomic number of scandium is 21. It is also a transition element but it doesn’t show variable valences. Its electronic configuration is [Ar-]3d14s2. So, its valency is 3. 

  10. Vanadium – Atomic number of Vanadium is 23. It is also a transition element that shows variable valances. Its electronic configuration is [Ar-]3d34s2. It shows valences 2,3,4 and 5 (majorly 5 & 4).


Valency Chart of Elements 

The valency chart of the first thirty elements is given below along with their atomic number.


Element

Atomic Number 

Valency 

Hydrogen

1

1

Helium 

2

0

lithium

3

1

Beryllium 

4

2

Boron

5

3

Carbon

6

4

Nitrogen

7

3

Oxygen

8

2

Fluorine

9

1

Neon

10

0

Sodium

11

1

Magnesium

12

2

Aluminum

13

3

Silicon

14

4

Phosphorus

15

3

Sulphur

16

2

Chlorine

17

1

Argon

18

0

Potassium

19

1

Calcium

20

2

Scandium

21

3

Titanium

22

2,3,4

Vanadium

23

5,4

Chromium

24

2,3

Manganese

25

2,3,4,5,6,7

Iron

26

2,3,4,6

Cobalt

27

2,3,4

Nickel

28

3,2

Copper

29

2,1

Zinc 

30

2


Use of Valency

The valency or valency chart is helpful in order to determine how many atoms of an element will combine with another element to form any chemical formula. Another important use of valency of elements is to find or deduce formulae of compounds. If we know the valency of elements, then we can easily write formulae of compounds of those elements. For example – 

  • The formula of compound carbon tetrachloride – 

The symbol Carbon is C and chlorine is Cl. Their valencies are 4 and 1, respectively. The formula  of compound carbon tetrachloride will be CCl4 as

Chlorine will lose one electron and carbon will gain four-electron in order to complete its octet.

  • The formula of compound magnesium chloride –

The symbol of magnesium chloride is Mg and chlorine is Cl. Their valancies are 2 and 1 respectively. 

The formula of magnesium chloride will be MgCl2 as magnesium will lose two electrons and chlorine will gain one electron in order to make a compound.

Valency  2

  • The formula of compound hydrogen chloride –

The compound hydrogen chloride is formed by hydrogen and chlorine both of the elements have valency  1. Hence they will make a compound of chemical formula HCl.

Valency  1    2

Formula: H2S

Hence the valency chart is essential for the writing of formulae of compounds. We get all the necessary information related to valency through this article. If you want to learn more about valency or you are confused between valency and oxidation number then register yourself on Vedantu or download Vedantu learning app for Class 6 -10 IIT JEE & NEET and get detailed study notes for all topics of chemistry, NCERT Solutions, Mock tests, Revision notes etc. You can also check another article ‘Valency’ available on Vedantu for more information about the topic.