Calculate the percent ionization of formic acid in a solution that is 0.152 M in formic acid. The Ka of formic acid is 1.77 × 10 -4.​

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.