Determine how many electrons are in the last level of the Ca atom.

CA-element of the main subgroup of the second group, element number 20
if we know the element number, then we know the total number of atoms. only 2 atoms can always be located at the first level, then we simply consider:
Level 1: 2 atoms
Level 2: 8 atoms
Level 3: 3 atoms
Level 4: 2 atoms
* – 4 levels because Al is in the 4th period.