Question

Write the number of protons, neutrons and electronic configuration of \[\ce{_19^39K, _15^31P}\]. Also state their position in periodic table.

Answer 1

Atomic number = Number of protons

Hence, the number of protons in K atom = 19

Number of neutrons = Mass number − Atomic number

Hence, the number of neutrons in K atom = 39 − 19 = 20

Number of electrons = Number of protons

Hence, the number of electrons = 19

And electronic configuration of K atom = 2, 8, 8, 1

Since K atom has 4 shells, hence it belongs to fourth period.

With one valence electron, it belongs to group 1

Number of protons in P atom = 15

Number of neutrons in P atom = 31 − 15 = 16

Number of electrons in P atom = 15

And electronic configuration of P atom = 2, 8, 5

Since it has three shells, it belongs to period 3 and has 5 valence electrons. Phosphorus is found in five plus ten, which is the 15^th group.