Ncert Exercises & Solutions

For the electrons of an oxygen atom. The correct statement among the following is :

1.	Z_eff for an electron in a 2s orbital is the same as Z_eff for an electron in a 2p orbital.
2.	An electron in the 2s orbital has the same energy as an electron in the 2p orbital.
3.	Z_eff for an electron in 1s orbital is the same as Z_eff for an electron in a 2s orbital
4.	The two electrons present in the 2s orbital have same spin quantum numbers m_s but of opposite sign

Hint: Two electrons present in any orbital have spin quantum numbers m_s but of opposite sign, that is, \(\frac{-1}{2}\) and \( \frac{1}{2}\).

(a) Electrons in 2s and 2p orbitals have different screen effect. Hence, their Z_eff is different. Z_eff of 2s orbital>Z_eff of 2p orbital

Therefore, it is not correct.

(b) Energy of 2s orbital

Hence, it is not correct.

\neq

Z_eff of 2s orbital

Hence, it is incorrect.

(d) For the two electrons of 2s orbital, the value of m_s is

+ \frac{1}{2}

and

- \frac{1}{2}

Hence, it is correct.