Question

The valence level and valence, respectively, for calcium are?

4 and 2

2 and 4

4 and 4

3 and 2

2 and 2

A 4s-electron in K atom is lower than a 3d-electron due to The shape of the 3d-orbitals The fact that there are five 3d-orbitals A low ionization energy of K Penetration and shielding The relative sizes of 4s-orbitals and 3d-orbitals

Answer 1

1. Valence shell electronic configuration of Ca is: [Ar] 4s²

Thus, Valence level = 4

and number of valence electrons = 2

Hence, option a

2. According to Aufbau Principle, Electrons are added in an atom in its respective orbitals in order of increasing energy.According to Aufbau , (n+L) rule is followed. Lesser the (n+L) value, lesser is the energy and stable is the electron in it . Also. 4s has lower energy than 3d due to the shielding effect of inner electrons.

Shielding effect: It is also called screening effect in which inner electrons shield the outer electrons from nuclear charge due to which net effective attraction is less than actual.

Penetrating power of 3d electron is more than 4s. Or the shielding effect of 4s is more than the 3d.

Hence Reason is penetration and shielding.