How many shells of electron does sodium have?

sodium has 11 electrons
2 are in its first shell
8 are in its second shell
only 1 electron is in its 3rd shell

How many shells of electron does sodium have? ........three
How many electrons are in the atom's 3rd shell?..........one
Is the 3rd shell full? ..........no
Is another shell needed? ...........no
anothe shell is not needed until you have an atom with 19 electrons, such as what potassium has