Question

What is the valency of potassium ion?

Answer 1

Hint: This question is asked from the basic concepts of chemistry. To solve this problem, you need to write the electronic configuration of potassium. The number of electrons required to lose or gain to achieve the noble gas configuration is the valency of the potassium.

Complete step by step answer:
We know that all the things in this world are trying to attain stability. Similarly, atoms are also trying to attain stability. We know that the noble gas atoms are the most stable atoms in the periodic table. The reason for this stability is it has eight electrons in their outermost shell. So, every atom will try to attain this configuration. In some cases, the atoms will need electrons and in some cases they need to remove electrons to attain this noble gas configuration. This number of electrons which needed to gain or lose is the valency of that atom. Now, let us check the electronic configuration of potassium:

The electronic configuration of potassium is 2, 8, 8, 1. Here, the last shell contains 1 electron and only eight electrons should be needed in the last shell. To achieve this, potassium can donate one electron and then it will become 8 electrons in the outermost shell. If potassium donates one electron and becomes potassium ion, the configuration will be 2, 8, 8.

So, the number of electrons that potassium needs to donate to attain stability is 1. Therefore, the valency of potassium is 1.

Note: To remove an electron from the outermost shell of an atom or gain an electron needs energy. The energy required to remove an electron is ionisation enthalpy and the energy required to donate electrons is electron gain enthalpy.