20. Select the false statement below. A) Generally speaking, as you go across a period in the periodic table, the effective nuclear charge (Zeff) increases because each successive element contains more protons in the nucleus than the previous element and the outer electrons are all in the same shell as you go across a period. B) Generally speaking, the heavier halogens can be predicted to exhibit greater shielding of the outer-shell electrons by the inner-shell electrons than lighter halogens. C) Generally speaking, non-metallic elements have less effective nuclear charge (Zeff) than metallic elements in the same period. D) Generally speaking, as you go down a group in the periodic table, there is successively greater shielding of the outer-shell electrons by the inner-shell electrons.

C) Generally speaking, non-metallic elements have less effective nuclear charge (Zeff) than metallic elements in the same period

Explanation:

Let us remember that metals are found towards the left hand side of the periodic table while nonmetals are found towards the right hand side of the periodic table.

The magnitude of effective nuclear charge increases from left to right in the periodic table as the size of the nuclear charge increases without a corresponding increase in the number of shells. This implies that as one moves from metals to nonmetals, there is a significant increase in the magnitude of effective nuclear charge which simultaneously leads to an increase in ionization energy across the period.

Therefore, it is a false statement that; 'Generally speaking, non-metallic elements have less effective nuclear charge (Zeff) than metallic elements in the same period'.

The statement that can be regarded as false is : C) Generally speaking, non-metallic elements have less effective nuclear charge (Zeff) than metallic.

Therefore, Periodic table has its arrangements in periods and group.

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