Classification Of Elements And Periodicity In Properties Question 160

Question: The statement that is not correct for periodic classification of elements is

Options:

A) the properties of elements are periodic functions 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.

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Answer:

Correct Answer: C

Solution:

[c] In case of transition elements (or any elements), the order of filling of electrons in various orbitals is $ 3p<4s<3d $ . Thus, 3d-orbital is filled when 4s orbital gets completely filled.