How to Use a Valency Chart: Quick Reference for Students
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.
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.
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.
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.
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.
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.
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.
Nickel – Nickel is a transition element. So, it shows variable valences. Its atomic number is 28. It shows valences 2,3 and 4 majorly.
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.
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.
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.
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.
FAQs on Valency Chart: Definitions, Examples & Uses
1. What is a valency chart and what information does it provide?
A valency chart is a reference table in chemistry that lists various elements and their combining capacity, which is known as valency. It essentially tells you how many chemical bonds an atom of a specific element is able to form with other atoms to create a stable compound.
2. How is the valency of an element generally calculated?
Valency is determined by the number of electrons in an atom's outermost shell, also known as valence electrons. A simple rule is:
- For elements with 1 to 4 valence electrons, the valency is typically equal to this number.
- For elements with more than 4 valence electrons, the valency is often calculated by subtracting the number of valence electrons from 8 (as per the octet rule).
3. What is the main purpose of using a valency chart in chemistry?
The primary use of a valency chart is to help write the correct chemical formulas for compounds. By knowing the valencies, you can determine the precise ratio in which elements must combine to form a neutral and stable molecule, like how two hydrogen atoms (valency 1) combine with one oxygen atom (valency 2) to form H₂O.
4. Is there an easy trick to learn valency without memorising the entire chart?
Yes, instead of memorisation, you can understand the patterns in the periodic table. For elements in the main groups, the valency is often related to their group number. For instance, Group 1 elements (like Sodium) have a valency of 1, and Group 17 elements (like Chlorine) also have a valency of 1. This method is much faster than rote learning.
5. What is the key difference between an element's valency and its oxidation state?
Valency is a number describing an atom's combining power and it does not have a sign (positive or negative). For example, carbon's valency is 4. In contrast, the oxidation state represents the hypothetical charge an atom would have in a compound and can be positive, negative, or zero. For instance, in methane (CH₄), carbon's oxidation state is -4.
6. Why do some elements, like iron and copper, show more than one valency?
Elements like iron (Fe) and copper (Cu) are transition metals. They have a special ability to lose electrons not just from their outermost shell, but also from the shell just inside it. This flexibility allows them to form stable bonds in different configurations, leading to variable valencies (e.g., iron can have a valency of 2 or 3).
7. Can an element's position in the periodic table predict its valency?
Absolutely. The periodic table is a great shortcut for determining valency for main group elements. For example:
- Group 1 elements have a valency of 1.
- Group 2 elements have a valency of 2.
- Group 17 (halogens) have a valency of 1.
- Group 18 (noble gases) have a valency of 0 because their outer shells are full.
8. Why is the valency of noble gases like Neon and Argon considered to be zero?
Noble gases have a completely filled outermost electron shell, which is a very stable electronic configuration. Because they are already stable, they have no tendency to gain, lose, or share electrons to form chemical bonds with other elements. Therefore, their combining capacity, or valency, is zero.
