Which of the following is a reasonable ground-state electron configuration?
a. 1s^2 2s^2 2p^6 3s^2
b. 1s^2 2s^2 2p^6 3s^2 3d^4
c. 1s^2 2s^2 2d^10 2p^3
d. 1s^2 2s^s 2p^3 2d^6

The answer to your question is: letter A.

Explanation:

To solve this question, we must consider the total number of electrons that can be placed in each orbital.

         Orbital                  Number of electrons

             s                                   2

             p                                  6

             d                                 10

             f                                  14

Options given

A. 1s² 2s² 2p⁶ 3s²                 This electron configuration is correct because

                                              is in agreement with the number of electrons

                                              allowed in each orbital and the correct order

                                             of them.

B. 1s² 2s² 2p⁶ 3s² 3d⁴          This electron configuration is incorrect because

                                              3d⁴ goes after 3p.

C. 1s² 2s² 2d¹⁰ 2p³                This option is incorrect because 2d¹⁰ does not

                                              exist.

D. 1s² 2s^s 2p³ 2d¹⁰            This option has 2 mistakes, s as a power does

                                              not exist and 2d¹⁰ is also incorrect.