Strong acids are generally either hydrohalic acids (ex. hcl) or oxoacids in which the number of oxygen atoms exceeds the number of ionizable protons by 2 or more (ex. hno₃).

Answer and explanation;Strong acids are generally either hydrohalic acids (ex. HCl) or oxoacids in which the number of oxygen atoms exceeds the number of ionizable protons by 2 or more (ex. HNO₃).Strong acids dissociate completely into ions in water. In a dilute solution of a strong acid, HA molecules are no longer present.  General strong acid dissociation in water equation: HA + H20 -> H3O+ + A- [H3O+] = [A-] = [HA]initial SO; [HA]eq = 0, and the Kc value is extremely large.   Strong acids are either;

-Hydrohalic acids, examples; HCl, HBr, HI

-Oxoacids in which the number of O atoms exceeds the number of ionizable protons by two or more, examples;  HNO3, H2SO4, and HClO4.

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.