The d sublevels are called 3d and 4d. The only f sublevel we study is the 4f. When we fill electrons into an atom, we start with the 1st level because it is closer to the nucleus and thus lower in energy.

What are the 4 sublevels?

Each sublevel is assigned a letter. The four you need to know are s (sharp), p (principle), d (diffuse), and f (fine or fundamental). So, s,p,d & f. The Principal Energy Level (the #) only holds that # of sublevels.

What sublevel is before 3d?

The position of atomic numbers 19 and 20 in the fourth row of the s block and the position of atomic numbers 21 through 30 in the first row of the d block show that the 4s sublevel fills before the 3d sublevel. Notice that atomic numbers 57 through 70 on the periodic table below are in the 4f portion of the table.