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 don't see a text, but i am gonna assume this *orbit* the curved path, usually elliptical, described by a planet, satellite, spaceship, etc., around a celestial body, as the sun.