1.14 Deduce the electronic configurations of the first 20 elements from their positions in the Periodic Table

The group number is the number of electrons in the outer shell. The atomic number is the number of protons, which is equal to the number of electrons (the charges need to balance each other out to make the atom neutral). It’s helpful to know that the first shell holds 2 electrons, the second holds eight, and the third holds eight as well. You can start filling up shell 4 if necessary but you don’t need to know how many this shell holds. So for example, Oxygen has an atomic number of 6 (and it’s in group 6) so its electronic configuration is…

2, 4