Question

How does the shielding effect affect trends?

Answer 1

Hint: Shielding effect is the phenomenon of the atomic world where the valence electrons are shielded from the attraction towards the nucleus of an atom. This can be seen more in 3d elements.

Complete answer:
Let us discuss the shielding effect and how it affects the general trends of modern periodic table;
As we know that the shielding effect is the resistance to the attraction of the electrons towards the nucleus. This increases down the group as the atomic radii also increases and remains the same in the period.
This effect is due to the constituent electrons only; the electrons present in the middle of the nucleus and valence electrons act as shields which repel those outer electrons. This lowers the effective nuclear charge.
The effect it causes on the trends of periodic table are;
More shielding $\to $ less electronegativity
More shielding $\to $ alkali earth metals becomes more reactive as we move down
More shielding $\to $ halogens become more reactive as we move upwards.

Note:
The shielding effect describes the point that how easily we can remove the electron from the atom making it more reactive at normal conditions.