Periodic Table, Periodic Properties and Variations of Properties — Question 15

For $_{19}^{39}\text{K}$:

No. of Protons = 19

No. of Neutrons = 39 - 19 = 20

Electronic Configuration = 2, 8, 8, 1

Position in periodic table = 4^th period (as it has 4 shells) & 1^st group (as it has one valence electron).

For $_{15}^{31}\text{P}$:

No. of Protons = 15

No. of Neutrons = 31 - 15 = 16

Electronic Configuration = 2, 8, 5

Position in periodic table = 3^rd period (as it has 3 shells) & 15^th group (as it has five valence electrons).