Question

The statement that is not correct for periodic classification of elements is ______.

Options

• The properties of elements are periodic function of their atomic numbers.

• Non metallic elements are less in number than metallic elements.

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

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

Answer 1

The statement that is not correct for periodic classification of elements is for transition elements, the 3d-orbitals are filled with electrons after 3p-orbitals and before 4s-orbitals.

Explanation:

For transition elements, the 3d-orbitals are filled with electrons after 3p and 4s-orbitals and before 4p-orbitals. The order of filling the orbitals is 2s, 2p, 3s, 3p, 4s, 3d4p, 5s, 4d, 5p, 6s, …