Type the symbols for the elements listed below.

magnesium
potassium
iron
lead

The atomic symbol for Magnesium is Mg
The atomic symbol for Potassium is K
The atomic symbol for Iron is Fe
The atomic symbol for Lead is Pb

Idid the calculation and i get 875,000,000 which can be written as 8.75 x 10^6?

The problem here is that according to aufbau principle before 3d orbital 4s subshell comes.after filling 3p orbital with electrons you have 4 electrons left, you place two in 4s with opposite spin and the other two in 3d in any of its two orbitals of total five orbitals with the same spin.