Given the following, how many protons are in an atom of chlorine? What is the atomic number of sodium?

Hint: The atomic number of the chemical element is equal to the number of protons present in the nucleus of an atom. The chlorine atom contains 6 more protons than the sodium atom. The number of electrons is the same as the number of electrons.

Complete step by step answer:
The chlorine is a chemical element present in group 17 of the periodic table. It is a halogen atom. The sodium is the chemical element present in group 1 of the periodic table. It is an alkali metal.
The atomic number is defined as the number of chemical elements present in the periodic table where the elements are placed according to the increasing number of protons.
The atomic number of the atom is denoted by Z which is the same as the number of protons in the nucleus present in the atom and also the number of electrons in the neutral atom is the same as the number of protons.
The atomic number of chlorine is 17 so the number of protons present in chlorine atoms is 17. The electronic configuration of chlorine is $[Ne]3{s^2}3{p^5}$. The total number of electrons in chlorine atoms is 17 and the valence electrons in chlorine is 7.
The atomic number of sodium is 11 and the number of protons present in sodium is 11. The electronic configuration of sodium is $[Ne]3{s^1}$.

Note:
The atomic number of chlorine is 5 times less than the twice of the atomic number of sodium which is calculated as
$\Rightarrow 2 \times {Z_{Na}} - 5$
$\Rightarrow 2 \times 11 - 5$
$\Rightarrow 22 - 5$
$\Rightarrow 17$