Question

what is nuclear charge of an element and how it effect the atomic size

Answer 1

The nuclear charge is the total chargeof all the protons in the nucleus. It has the same value as the atomic number. The nuclear charge increases you go across the periodic table.
And its effect
For all elements except H, the effectivenuclear charge is always less than the actual nuclear charge because of shielding effects. The greater the effective nuclear charge, the more strongly the outermost electrons are attracted to the nucleus and the smaller the atomic radius

Answer 2

The nuclear charge is the total charge of all the protons in the nucleus. It has the same value as the atomic number. The nuclear charge increases you go across the periodic table.

Higher Nuclear Charge = Smaller atom

Essentially, a higher nuclear charge means that the strength of the nucleus (protons) is stronger. Because of this, the electrons around the nucleus are pulled in more. And since electrons make up most of the volume of an atom since they're the ones moving around, the atom's volume decreases.