Question

What is the abbreviation for calcium?

Answer 1

Element Name: Ca
or
Electron configuration: [Ar] `4s^2`

I wasn't actually sure which one you meant.

Explanation:

Group two, period four, holds Calcium as Ca with an atomic number of 20.

If you needed the electron configuration, it would be `1s^2` `2s^2` `2p^6` `3s^2` `3p^2` `4s^2`

and when you're abbreviating that, you take the last noble gas it had passed; Ar.

Then, fill in until you get to the Ca. Which would look like: [Ar] `4s^2`