Give a characteristic to the element with the number of protons in the nucleus equal to 20.

A chemical element with 20 protons in its nucleus is Ca (calcium)
He is in the fourth period (large), in the second group (main subgroup)
Serial number 20
Relative atomic mass = 40
Atom structure:
Core Charge +20
+ 20Ca) 2) 8) 8) 2
Electronic formula: 1s2 2s2 2p6 3s2 3p6 4s2
At the last energy level there are 2 electrons, the level is not complete.
The number of electrons is 20, the number of protons is 20, in order to calculate the number of neutrons, it is necessary to subtract the serial number 40 – 20 = 20 from the atomic mass, which means the number of neutrons is 20
The valence of calcium is (II), since the group number for the elements of the main subgroup shows its highest valency for oxygen.
Superior oxide: CaO
Hydroxide: Ca (OH) 2
It has no volatile hydrogen compound.