Question

In Boron atom, screening is due to:
(A) Electrons of K shell only
(B) All the electrons of K and L shell
(C) Two electrons of 1s and 2s each
(D) Only by electrons of L shell

Answer 1

Hint: Screening effect can also be known by the other name called shielding effect. This is the phenomenon which occurs when the nucleus reduces its force of attraction on the valence electrons due to the presence of electrons in the inner-shell.

Complete Step by step explanation: Boron is a chemical element represented by the symbol B having atomic number 5. Boron is a metalloid in nature. Electronic configuration of boron is shown by $1s^{2}2s^{2}2p^1$. Outer electrons experience attraction from the nucleus and repulsion from the inner electrons. As the attraction between the nucleus decreases, the repulsion increases between the inner electrons and outer electrons.
Electron shell of an orbit is followed by electrons around an atom’s nucleus. The closest shell to the nucleus is K-shell or 1st shell which contains 2 electrons. The 2nd shell is known by L-shell which can hold up to 8 electrons and the third shell represented by M-shell contains 18 electrons. The general formula for the nth shell can hold $2n^2$ electrons.
Boron have electron arrangement K = 2; L = 3
Screening effect in boron is higher on the outermost electrons which causes less attraction from the nucleus and can be easily removed and leads to lower value of ionization potential.

Thus the boron screening effect is due to two electrons of 1s and 2s subshells.

Note: Ionization potential is the amount of energy required to remove an electron from a molecule, Higher is the screening effect lower is the value of ionization potential.