1. Tardigrade
  2. Question
  3. Chemistry
  4. Which of the following statements are correct? (i) The second period (n=2) starts with lithium and third electron enters the 2 s orbital. (ii) Successive filling of 3 s and 3 p orbitals gives rise to the third period of 8 elements from sodium to argon. (iii) The fourth period (n=4) starts at potassium and the added electron fill up first 4 s and 4 p orbitals then 3 d orbital is filled. (iv) Fifth period begins with rubidium with the filling of 5 s orbital and ends at xenon with the filling up of the 5 p orbital.

Question Error Report

Thank you for reporting, we will resolve it shortly

Back to Question

Q. Which of the following statements are correct?
(i) The second period $(n=2)$ starts with lithium and third electron enters the $2 s$ orbital.
(ii) Successive filling of $3 s$ and $3 p$ orbitals gives rise to the third period of 8 elements from sodium to argon.
(iii) The fourth period $(n=4)$ starts at potassium and the added electron fill up first $4 s$ and $4 p$ orbitals then $3 d$ orbital is filled.
(iv) Fifth period begins with rubidium with the filling of $5 s$ orbital and ends at xenon with the filling up of the $5 p$ orbital.

Classification of Elements and Periodicity in Properties

Solution:

In fourth period filling up of $3d$ orbital becomes energetically favourable before the $4p$ orbital is filled.