Variable Valency: Definitions, Examples, Electrovalency, Causes, Facts, and Sample Questions

Variable Valency Overview

Elements rarely exist alone in nature; instead, they interact with one another. Valency is the capacity of one element to mix with another. Elements interact with one another to produce a stable state. It specifies the maximum number of electrons that an element may accept or give in order to achieve a stable electronic state.

What is Valency?

G.N. Lewis, a chemist, created Valency. An element's valency is its ability to combine. The amount of electrons provided or absorbed by an element's atom in order to have the electronic configuration of the next noble gas is referred to as its valency.

Variable Valency

Certain components have several valencies; these are known as variable valencies; compounds of this type have varying valencies in different combinations. Iron, mercury, and copper are examples of elements with varying valency. Transition elements are characterized by varying degrees of valency. Depending on the sort of interaction, different elements interact with other atoms in varying quantities, receiving, giving, or sharing electrons with them. The varieties of valency are as follows-

1. Ionic Compounds' Valency
2. Covalent Substances' Valency
3. Variable Valency

Variable Valency Examples

When iron combines with oxygen, for example, it produces ferrous oxide and ferric oxide, among other molecules. Variable valency is the name given to this occurrence. Transition metals with varying valencies include nickel, copper, tin, and iron.

Variable Electrovalency

Ionic bonds are formed when electrons are lost or added to an element's atom. This is referred to as the element's electrovalency. The s-block components have no changeable valency. The valency of P-block elements with higher atomic numbers and transitional inner elements is more varied. There are two major causes for varying valency. Inert pairs' effect on p-block elements. When it comes to inner transition elements, the energy difference between ns and (n-1) d subshells, as well as ns and (n-2) d subshells, is quite small.

Inert Pair Effect

The oxidation state of the bulk of the elements in the III-A group is +3. However, as we progress through the group, the oxidation state +1 becomes more dominant. Similarly, the elements in the IV A group have a +4 oxidation potential in general, but as we descend the group, the +2 state becomes more dominant. The two electrons in the valence shell (ns2) tend to stay inactive when bonds are formed. This is known as the inert pair effect. As a result, inert pair effects are the principal cause of changing valency in p-block elements.

The Energy Distinction between Orbitals

The fluctuation of incompleted orbitals and electrons from the ns orbital in transition metals causes the oxidation state to vary. As a result, electrons from both energy levels can be bonded. Similarly, the valency of inner transition elements varies due to insufficient filling of f-orbitals. In addition to ns electrons, some f-orbitals can be used to form chemical bonds.

Causes of Variable Valency

The following are some of the causes of variable valency-

1. Because of differing electrical arrangements, certain elements have variable valency. It occurs as a result of electron transfer from one shell to another. 
2. The cause of the increased electron loss is due to particular electrons. 
3. The existence of unoccupied orbits in the same sub-shells causes electrons to jump from one shell to another. 

Read more about the Reactivity Series of Metals, Types of Hybridization, and Formal Charge Formula.

Elements Having Variable Valency

Transition metals with varying valencies include nickel, copper, tin, and iron. Non-metallic elements with variable valencies include nitrogen and oxygen. When various valency atoms react, the products they form have varied qualities. The following table gives details about the various elements having variable valency-

Facts about Variable Valency

1. The bonding potential of the elements is represented by valency.
2. The fixed attribute of items is their basic value.
3. Valency's value can never be 0.

Metals with Variable Valency Representation

It is usual to employ a Roman number as a superscript next to an element's symbol to denote its changeable valency. For metals, the suffix 'ous' represents the lower valency, while the suffix 'ic' represents the greater valency, in this order- 

For example, the valency of iron is between two and three. As a result, we write ferrous (Fe²⁺) to represent the lower valency (2), and ferric (Fe³⁺) to indicate the higher valency (3).

The current technique, on the other hand, employs Roman numerals to describe an element's changeable valency. As a result, we use Fe (II) for ferrous and Fe (III) for ferric.

Read more about the First 20 Elements of the Periodic Table.

Non-Metal with Variable Valency Representation

The valency of a nonmetal is dictated by the number of other atoms connected to it. Phosphorus and potassium, for example, contain three and five valence electrons, respectively. It forms two molecules when coupled with chlorine-

1. PCl³ 
2. PCl⁵

In the structure of phosphorous trichloride, three electrons are shared by phosphorous and three chlorine atoms, resulting in the element possessing valency 3. Because pentachloride possesses five electrons, it has a valency of five.

Conclusion

A particular element's valency can alter depending on the circumstances of a chemical reaction. Metals, in general, donate electrons from their outer shells to produce positively charged ions. Some metals' valence shells, on the other hand, lose electrons. The element in this situation has a variable number of valence electrons and different electropositive valencies.

Points to Remember

1. According to Hund's rule, electrons first fill shells with parallel spins before filling them with antiparallel spins.
2. Elements are more stable in a d-shell. 
3. Shell 1 has subshells, Shell 2 has two subshells, s, and p, and Shell 3 has s, p, and d.
4. The atomic numbers enhance the variable valency. 
5. The elements in the s-block (sodium, calcium, and magnesium) do not have varying valencies. 
6. The valency of the elements in the halogen group is 1. The value will be 0 when the K shell is entirely filled. 
7. When the d-block components have variable valency, they are half-filled. When such elements' orbitals are complete, they do not exhibit changing valencies. Cadmium, for example, does not have a variable value. 

Sample Questions for Variable Valency

Sample Question 1: Is gold's value variable?

Solution: It is indeed. It has two values: 1 and 3. 

Sample Question 2: What is the iodine tendency?

Solution: Iodine has an electron-accepting propensity. It has a valency of 1. 

Sample Question 3: What exactly is variable valency?

Solution: The ability of elements to represent multiple valencies in distinct compounds is referred to as variable valency. Variable valency, as the name implies, lacks a defined pattern. The electrical configuration of any element is required to get its variable valency. Variable valency occurs when a chemical has various vacancies.

Sample Question 4: What are two items with varying valency?

Solution: The two components are iron and silver.

Sample Question 5: Which of the following elements has no valency?

Solution: Argon has no valency. 

Sample Question 6: What is the steady valency of iron?

Solution: Iron has a more stable valency of three. Because the d - blocks are half-filled, they have a greater probability of forming a robust configuration, making the configuration stable.