Answer: [tex]Ca:20:1s^22s^22p^63s^23p^64s^2[/tex]
[tex]Ar:18:1s^22s^22p^63s^23p^6[/tex]
Explanation:
Electronic configuration represents the total number of electrons that a neutral element contains. We add all the superscripts to know the number of electrons in an atom. The electrons are filled according to Afbau's rule in order of increasing energies.
The electronic configuration for element Ca with atomic number 20 and thus 20 electrons is:
[tex]Ca:20:1s^22s^22p^63s^23p^64s^2[/tex]
The electronic configuration for element Ar with atomic number 18 and thus 18 electrons is:
[tex]Ar:18:1s^22s^22p^63s^23p^6[/tex]
