How was neutron discovered?

What does the atomic number of an element tell about the element?

Write down the electronic configuration of the following:

Oxygen (Atomic number $=8$).

Write down the electronic configuration of the following:

Phosphorous (Atomic number $=15$).

Write down the electronic configuration of the following

Calcium (Atomic number$=20$)

Write down the electronic configuration of the following

Silicon (Atomic Number$=14$)

Give the nuclear structure and the distribution of electrons of the following element:

Nitrogen.

Give the nuclear structure and the distribution of electrons of the following element:

Fluorine.

Give the nuclear structure and the distribution of electrons of the following element:

Aluminium.