Which of the following statements about effective nuclear charge for the outermost valence electron of an atom is incorrect?

(i) The effective nuclear charge can be thought of as the true nuclear charge minus a screening constant due to the other electrons in the atom.

(ii) Effective nuclear charge increases going left to right across a row of the periodic table.

(iii) Valence electrons screen the nuclear charge more effectively than do core electrons.

(iv) The effective nuclear charge shows a sudden decrease when we go from the end of one row to the beginning of the next row of the periodic table.

(v) The change in effective nuclear charge going down a column of the periodic table is generally less than that going across a row of the periodic table.