Valency and Its Calculation

Valency is an important topic in chemistry, especially for Class 9 students. Valency is one of those topics in chemistry that students are very well aware of because of its part in forming chemical compounds or molecules. For starters, let us take the example of water, the chemical formula of water is H2O, and the question is, why do we write it as H2o. The answer to this question is because of valency.

The concept of valency can be overwhelming for students, and they often take time to understand the concepts related to the topic and how to calculate them. There is no need to worry about that, as this post explains the fundamentals of valency and the different ways to calculate valency. Read on to find out more about valency.

What is Valency?

Valency, in simple terms, is the measurement of the combining capacity of atoms and molecules. There are bonds that an atom forms as a part of a compound, and that bond is expressed by the valency of the element.

Now, let us look at the concept of valency. There are electrons present in an atom, and they are arranged in different orbitals or shells, which are represented as K, L, M, and so on. The number of orbitals in an atom depends on the atom and its chemical composition. The electrons present in the outermost orbit are called valence electrons and take part in any chemical reaction because the outer orbital contains the most energy compared to other orbitals.

Uses of Valency

Students often ask why is valency essential or why is it used. Well, the uses of valency are fundamental in the field of chemistry. The benefits of valency are as follows:

• One of the most important uses of valency is that it helps to determine a chemical formula of a compound.
• The other use of valency is that it helps to determine the number of atoms of an element that will combine with another element to form a compound chemical formula.

Complete Octet in Valency

The Bohr-bury scheme states that the outermost orbit of an atom has a maximum number of 8 electrons. An atom whose outer orbit is said to have achieved a complete octet in valency. However, if the outermost ring of an atom is filled with the maximum number of electrons, then very little to no chemical activity can be observed. 

So, going by the above statement, an atom must gain or lose electrons to achieve a complete octet. For instance, hydrogen (H2O) has 1 electron in its outer orbit, so it must lose 1 electron to achieve a complete octet. So, the valency of hydrogen is 2. Moreover, helium has 2 electrons in its outer orbit, so helium has to lose 2 electrons. Hence its valency is 2. Students can find more examples of valency in the image below to get a better idea.

How to Calculate Valency?

There are different ways to determine or calculate valency. The steps to calculate valency is not hard, and students can get a good idea of determining valency by putting enough determination and focus into the steps. The different ways of determining a valency are:

• Octet rule: As already mentioned, the octet rule is one of the most used ways to calculate valency. As already said, an atom has a maximum of 8 electrons in its outermost orbit or shell, and a compound is stable when the outermost orbit is filled to its maximum. When the outermost orbit has 1 to 4 electrons, it is said to be positive valency because it donates these electrons to have stability. On the other hand, if an atom has 5 to 8 electrons, the valency is determined by adding more electrons to its outermost orbit.
  
• Periodic Table: One of the simplest ways of determining and calculating valency is through the periodic table. The arrangement of the periodic table is key to determining valency. For instance, all the elements in column 1 on the periodic table have 1 valency. Moreover, all elements in column 17 add 1 valency to their outermost orbit and so on. The noble gases column has a complete octet, meaning they have 8 electrons except helium, which has 2 valencies.
  
• Chemical Formula: This method of determining and calculating the valency is based on the octet rule. It is done by observing the chemical combination of an element. For instance, let us look at sodium chloride (NaCl). Here, sodium (Na) has the valency of 1 because it has to gain one electron because of its chemical compound. On the other hand, Chlorine has to lose one electron, so its valency is 1.

Difference Between Valency and Oxidation State

Students often confuse between valency and oxidation state. However, there is a vast difference between valency and oxidation states. The main difference between valency and oxidation state is valency is the number of electrons the outermost orbit of an atom loses or gains, and oxidation state is the charge that an atom can carry. For example, the valency of helium is 2 since it loses two electrons and the oxidation state is zero.

We hope that this detailed post on Valency and Its Calculation has helped you clear your doubts. If you have any questions or queries feel to contact us and we will try to answer at the earliest.

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