The effective nuclear charge of an atom is primarily affected by

The effective nuclear charge (ENC) of an atom is affected primarily by inner electrons.

The net positive charge imparted to an electron of a polyelectronic atom is known as the effective nuclear charge (ENC).

The formula is:

,

Where = effective nuclear charge,

Z = nuclear charge, and

S = average number of electrons between the electron and the nucleus.

The outer electron has no influence on S since only the inner electron is counted.

Thus, Inner electrons would be responsible for primarily affecting the effective nuclear charge of an atom.

To learn more about effective nuclear charge, refer to the link:

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a rain shadow is a dry region of land on the side that is protected against the prevailing winds of a mountain range. the prevailing winds are the winds that occur most of the time in a particular place of the earth

prevailing winds carry air toward the mountain range. as the air rises up over a mountain range, the air cools, water vapor condenses, and clouds form. on this side of the mountains, called the windward side, precipitation falls in the form of  rain  or snow. this dry air produces a  rain shadow.