Calculation of Valency from the Formula

Valency is the capacity of an atom or molecule to bond and interact with other elements. The greater the number of valence electrons, the more reactive the molecules or atoms are.

How Many Electrons in Each Orbital?

Electrons are in the most stable location first. The orbital that is inner (K) can hold at least 2 electrons. Another orbital (L) can hold eight electrons. The next orbital (M) also can hold eight electrons.

There are s and p, d and the f sub-orbitals, which are located inside the K M, N orbitals.

The presence of eight electrons within the L orbital gives stability due to the orbital being complete. With 2 electrons in the sub-orbital s and two for each of the three sub-orbitals of p creates the L orbital fully. This is also true for the M orbital too. This is known in “the Octet Rule.” For this, we can use the calculation of valency from the formula. 

Calculation of Valency from the Formula

Utilise your periodic table to locate the number of atoms or have the calculation of valency from the formula. In the first instance, we will use carbon. The atomic code is 6, which translates to six protons and six electrons.

The electron’s orbital is composed of 2 electrons. Therefore, the next orbital contains 4 (6 – 2, 4).

The outer orbital, which has four electrons moving in various ways, and circling the nucleus, could make four single bonds.

It is said that the carbon valency is 4. In this way, we can have the calculation of valency from the formula.

Periodic Table Groups

The periodic table arranges elements according to a particular order based on how they behave. Elements that have the same number of valence electrons possess similar properties. The groups are identified by the element that is high in the column of the periodic table.

It is believed that the Group 1A Lithium Family has one valence electron. The atoms of this section of the periodic table are prone to lose one electron and then bond it to an atom that prefers to take one electron.

The elements in the Beryllium group contain 2 electrons of valence, and elements of the Oxygen group possess 6. As per the pattern of elements wanting an entire shell of electrons, the oxygen group elements want to acquire 2 electrons.

The Helium Family, also called the Noble Gases, are non-reactive because they don’t have openings in their electron shell.

The value of elements like iron, which are part of the group of metals, can be more intricate and could be different depending on the force of other atoms surrounding it. 

Some elements have valency +2 under certain conditions, while it could be +3 under other circumstances. One of the causes of this variation is in larger molecules. The orbitals are more distant from the nucleus. This means that the force which connects an electron to the atom is less powerful. Another reason could be that the orbitals can be close to one another or overlap.

Valency of First Twenty Elements

For the calculation of valency from the formula, we will need the valency of the first twenty elements.

What are the various ways to determine the valency?

There are many methods to determine the valency of an atom, which are:

• Octet rule: As per the Octet rule, a substance is considered to be stable if its exterior shell contains eight electrons. When the amount of electrons within the outer shell ranges between one and four, the compound is thought to be of positive valency. 

If a compound has electrons that are four or five, six and seven, the value of the compound is measured by subtraction of the electron by eight. All noble gases, except for Helium contain eight electrons.

• Periodic table: A periodic table is composed of elements that are organised in a manner that the valency of any element can be determined. In column 1, metals have a value of +1 whereas the noble gas in column 18 possess a value of 0 . They are also inert.
• Valency derived from the chemical formula: This rule is built on the octet rule and is based on the observation of the combination of elements and its valency that can be established.

So, these are the methods or ways to calculate the value.

Valency derived from the formula

Valency is the capacity to combine one element with another.

1. Chlorine atoms combine with one atom of hydrogen to create HCl (hydrogen chloride) The chlorine valency is therefore 1.
2. 1 atom of carbon is combined with four hydrogen atoms to create CH4 (methane). Carbon’s valence is 4.

Conclusion

The power to combine or the capacity for an element can be referred to as its “valency.” It is used to determine the way in which the atoms of an element mix with the atoms from another element to make an organic compound.

The atoms that have one or two, three and four electrons of valence usually are lost to the combining of atoms and display the valences of one, three or four, accordingly. Atoms with 5, 6 or 7 valence electrons usually comprise 3, 2 or 1 electrons from the atoms of other elements, and display the three valences of 1.