Question

If the screening effect is not considered, and thus effective nuclear charge is the atomic number then the larger radius out of $Li,\text{ }Na$ is $11.$ (Consider only atomic number).

Answer 1

Hint : We know that the shielding effect is when the electron and the nucleus in an atom have a decrease in attraction which changes the nuclear charge. Screening effect is also known as the shielding effect.

Complete Step By Step Answer:
Ionic radii- The ionic radius is half the distance between atomic ions in a crystal lattice. To find the value, ions are treated as if they were hard spheres. The effective nuclear charge nuclear charge is the charge exerted by the nucleons i.e. protons and neutrons. For elements having fewer atomic numbers, there is no significant difference between effective nuclear charge and nuclear charge. But when the atomic number increases, shells get bigger and s, p, d, and f orbitals are involved due to the penetration effect of the inner orbitals, the total charge of the nucleus is shielded. So something less than the actual nuclear charge is exerted which is called Effective Nuclear Charge. The penetration effect is opposite to the shielding effect orbital has the highest shielding power and d orbital has less shielding power due to double-lobed structure.
This phenomenon occurs when the nucleus reduces its force of attraction on the valence electrons due to the presence of electrons in the inner-shell. The atomic number of $Li$ is $3$ whereas that of $Na$ is $11.$ The effective nuclear charge of sodium is higher so its atomic radius should be small. But a new shell is added for sodium. Hence, its atomic radius is large.

Note :
Remember that we should also know that Ionic radius increases as the screening effect increases. Hence, Ionic radius is directly proportional to the screening effect. Penetration effect is the penetration of nuclear charge through the orbitals which attracts the outermost shell electrons.