What is the electron configuration of an element with atomic number 20?

a. 1s^2 2s^2 2p^6 3s^2 3p^5

b. 1s^2 2s^2 2p^6 3s^2 3p^6

c. 1s^2 2s^2 2p^6 3s^2

d. 1s^2 2s^2 2p^6 3s^2 3p^6 4s^2

e. 1s^2 2s^2 2p^6

D

Explanation:

according to the aufbau principle the electrons should be filled

i think it's c. i'm not sure but i think so.

it should have an internal chamber and two thermometers sticking out of the top. the internal chamber will also be closed off from the outside.