The correct answer is option A: mass number
All of these factors affect the effective nuclear charge except mass number.
In physics, an atom has a dense positive-charged nucleus that exerts a definite amount of force on the electrons.
In a multi-electron atom, electrons move around the nucleus and experience a force that attracts them toward the center of the atom.
Outermost electrons are attracted by the positively charged nucleus however, the electron in the internal orbits exert an equal amount of force that negates the force of attraction of the nucleus.
There are many factors that affect the nuclear charge including electrons charge, charge on the nucleus, the distance between the nucleus and electrons, and the kind of orbital occupied by the electron.
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