The screening effect, also known as shielding, refers to the reduction in the effective nuclear charge experienced by an electron in an atom due to the presence of other electrons. This effect arises because electrons repel each other due to their negative charges.
The screening effect increases with an increase in the atomic number of an element. This is because as the atomic number increases, the number of electrons in the inner shells or energy levels also increases. These inner-shell electrons shield the outer-shell electrons from the full positive charge of the nucleus.
As a result, the outer-shell electrons experience a reduced effective nuclear charge, which weakens the attractive force between the nucleus and the outer-shell electrons. This reduction in the effective nuclear charge leads to larger atomic radii and affects various atomic properties, such as ionization energy and electron affinity, among others.
In summary, the screening effect increases with atomic number as more inner-shell electrons contribute to shielding the outer-shell electrons from the positive charge of the nucleus.