Question

Account for the following: (i) The effective nuclear charge (Z*) of element increase from left to right across the period and increase slightly down the group.

Answer 1

Answer:

Effective nuclear charge is the attractive positive charge of nuclear protons acting on valence electrons. The periodic table tendency for effective nuclear charge:

Increase across a period

Decrease down a group

Hence the reverse trend would be the Atomic mass which decrease down the period and increase down the group