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Well, everytime that you move from the left to the right, you jump orbitals. S orbitals can only hold 2 electrons. Those, such as Mg (magnesium) has an electron configuration of: \[1s^2 2s^2 2p^6 3s^2\] When you move to elements such as bromine, carbon, nitrogen, and those below it, they are in the P-orbital. The p-orbitals can hold up to SIX electrons. Since it is in the farthest, 6th position. For instance, Neon [Ne] has an electron configuration: \[1s^2 2s^2 2p^6\] however, carbon has: \[1s^2 2s^2 2p^2\] meaning that it's p-orbital only has 2 electrons in it's orbital shell. Now, with this information, try and do it for Ca (calcium). I am not sure if your teacher would like, but you can also use:\[[Ne]3s^2\] for magnesium the [Ne] basically just means represents the electron configuration for everything behind neon, which i wrote before. It's shorrt-hand notation, basically.