How many p-orbitals are occupied in a K atom?

Potassium (`"K"`) is located in group 1, period 4 of the periodic table and has an atomic number of 19.

Since you're dealing with a neutral atom, the number of electrons `"K"` has must equal 19. You could determine how many p-orbitals are occupied in a `"K"` atom by writing its electron configuration

`"K": 1s^(2) 2s^(2) 2p^(6) 3s^(2) 3p^(6) 4s^(1)`

As you can see, the 2p and 3p sublevels each hold six electrons, which means that they are completely occupied. Since every p sublevel has a total of three p-orbitals - `p_x`, `p_y`, and `p_z` - the number of p-orbitals occupied in a `"K"` atom is equal to 6 - 3 p-orbitals on the 2p sublevel and 3 p-orbitals on the 3p sublevel.

A faster way to figuring out how many p-orbitals are occupied in a `"K"` atom is by looking at the periodic table. The periodic table is split into blocks, as you can see here

http://imgarcade.com/1/spdf-periodic-table/

So, all you have to do is read the periodic table from left to right across each period - much like you would a sentence - until you get to potassium.

If you do this, you'll notice that you've passed two p sublevels: the one that starts at `"B"` and ends at `"Ne"` - the 2p sublevel - and the one that starts at `"Al"` and ends at `"Ar"` - the 3p sublevel. Once again, the conclusion is that `"K"` has 6 p-orbitals which hold 12 of its 19 electrons.

http://www.chemguide.co.uk/