Question

The outermost shell of an atom is known as:

Answer 1

The atom comprises protons, electrons and neutrons. Protons and neutrons are present inside the nucleus while electrons rotate around the atom. The electrons repel each other and so they are not present together like the nucleons. They are present in different shells.

Complete step by step solution:
- Atomic number gives the information about the number of protons as well as the number of electrons. So we can say that
Atomic number = no. of electrons = no. of protons
-After a lot of experiments, atomic structure was proposed and the probability of electrons were found to be maximum in a space known as orbital. Based on further studies, 4 quantum numbers were proposed which were able to give a complete picture of the electron location.
-Principle quantum number represents the shell of the electrons. It is represented by n. It gives a complete picture of shells and also the number of sub-shells. Value of n is always in natural numbers. First shell is denoted as K, second as L, third as M and fourth as N. Number of subshells is given by value of n and of orbitals by ${{n}^{2}}$ .
-So we see that there are many shells of an atom. The shell farthest from the atom is called the valence shell. It is the outermost shell of the atom and the electrons present in this shell are called the valence electrons.
-So, valency is the number of outermost electrons of the atom. It states the combining capacity of the atom. It can be found if we know the atomic number of an atom as it tells us the total number of electrons present in the atom.
-The number of electrons to be filled in each shell depends on Aufbau’s principle and Hund’s rule. Valency tells us only the total number of electrons present in the outermost shell of the atom and so it is different from the atomic number.

Therefore, the outermost shell of an atom is known as valence shell.

Note: Valency is the number of the electrons present in the outermost shell of an atom which is also called the valence shell of atom. Those electrons are important to be studied as they have the least attractive force from the nucleus and can easily be lost.