Make a schematic atomic structure of magnesium and phosphorus.

(Given number of protons of magnesium $=12$ and that of phosphorus$=15$ )

Answer the following question:

State the three observations made by Rutherford on his $\alpha$-particle scattering experiment.

Answer the following question:

Write the electronic configuration of an element whose mass number is 31 and atomic number is 15. What is its valency ?