What is effective nuclear charge?

Effective nuclear charge is a concept in chemistry that refers to the net positive charge experienced by an electron in a multi-electron atom. It is influenced by both the number of protons in the nucleus and the shielding effect of inner electron shells.

The effective nuclear charge is calculated by subtracting the effects of shielding electrons from the total number of protons in the nucleus. This results in a lower effective charge than the actual nuclear charge, due to the repulsive forces between electrons and the attraction of the nucleus.

The effective nuclear charge increases as you move across a period in the periodic table, due to the increasing number of protons in the nucleus. It also increases as you move down a group, due to the addition of new electron shells which provide more shielding.

Understanding the effective nuclear charge is important in predicting the chemical behavior of elements, as it influences properties such as ionization energy, electron affinity, and atomic size. Elements with a higher effective nuclear charge tend to have higher ionization energies and smaller atomic sizes.