Q. 65.0( 2 Votes )

The statement that is not correct for periodic classification of elements is:
A. The properties of elements are periodic function of their atomic numbers.

B. Non-metallic elements are less in number than metallic elements.

C. For transition elements, the 3d-orbitals are filled with electrons after 3p-orbitals and before 4s-orbitals.

D. The first ionisation enthalpies of elements generally increase with increase in atomic number as we go along a period.

Answer :

3d orbitals are filled after 4s in transition elements.

The modern periodic table is based on the properties that elements are a periodic function of their atomic numbers and once in a period an atom attains a stable configuration then the next element which occurs in the group shows similar properties as that of the element in the same group but of the previous period. This shows that option i) is correct.

The ionisation enthalpies increase as we move along the period due to increase in the effective nuclear charge. Thus option iv) is also correct.

This periodic table clearly shows that metals are more in number than non-metals. So option ii) is also correct.

Hence, the correct answer is (iii).

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