Question

What is the valency of copper in $C{{u}_{2}}O$?

Answer 1

Hint: Valence electron can be defined as the electrons present in the outer shell of an atom which can participate in the formation of chemical bond and this combining capacity of any atom is known as valency of that atom.

Complete answer:
Valence electrons can be calculated with the help of electronic configuration of an atom like the electrons present in the outermost shell. To know about this we first have to know the concept of electronic configuration. In this we fill the electrons according to three known rules called Aufbau principle, Pauli Exclusion Principle and Hund’s rule which describes how electrons are filled step by step. Like in s subshell only 2 electrons can be filled, in p subshell at most 6 electrons, d subshell 10 electrons and in f subshell only 14 electrons are present.
Valency in this compound is generally calculated by knowing the oxidation state of oxygen atom as we know that oxidation of oxygen is given by its valence i.e. from its configuration $1{{s}^{2}}2{{s}^{2}}2{{p}^{4}}$ i.e. have -2 oxidation state the valency of copper can be calculated as: $2x-2=0$i.e. 1 which shows the valency of copper in $C{{u}_{2}}O$ is one. The main difference between oxidation state and valency is valency can-not be negative whereas oxidation state can be.

Note:
The number of valence electrons in an atom tells us about their bonding behavior. Due to this reason elements whose atoms have the same number of valence electrons are grouped together in the periodic table of the elements.