Which of the following trends is indirectly proportional to effective nuclear charge, Zeff

-ionization energy

-electron affinity

-atomic size

-all answers are correct

Periodic trends provides information about an element’s properties. One major trends in the periodic table is the atomic size, which is indirectly proportional to effective nuclear charge. The atomic size gradually decreases from left to right across a periodic table because all electrons are added to the same shell. At the same time, protons are also added to the nucleus, making it more positively charged.

Due to this, there is a greater nuclear attraction; the effect of increasing proton number is greater than that of the increasing electron number, which means that there is a strong attraction of nucleus manifested by pulling the atom's shell closer to the nucleus. Then, the valence electrons are seized closer towards the nucleus of the atom, which resulted to the decrease in atomic radius.