Ncert Exercises & Solutions

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

1.	The properties of elements are periodic function of their atomic numbers
2.	Non-metallic elements are less in number than metallic elements
3.	For transition elements, the 3d-orbitals are filled with electrons after 3p-orbitals and before 4s-orbitals
4.	The first ionisation enthalpies of elements generally increase with increase in atomic number as we go along a period

Hint: The energy of 4s is lower than 3d
In case of transition elements (or any elements), the order of filling of electrons in various orbital is 3p<4s<3d. Thus, 3d orbital is filled when 4s orbital gets completely filled.

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