Question

What is the atomic number of helium?

Answer 1

We have to know that a chemical element that is represented by symbol is He is helium. We should know that helium is a Group $18$ element and it belongs to period $1$. We should know that helium belongs to the s-block and it is seen colorless. We know that the physical state of helium is gas.

Complete step by step answer:
We can define the atomic number or proton number of a compound component as the quantity of protons found in the core of each atom of that component. The atomic number remarkably recognizes a chemical component. It is non-distinguishable from the charge number of the core. In an uncharged molecule, the atomic number is additionally equivalent to the quantity of electrons.
We can say that electronic configuration of helium is $1{s^2}$. The electrons found in per shell of helium are $2$.
We know that the number of protons in Helium is two and the number of electrons in Helium is two. So, we saw that the atomic number is the quantity of proton found in the nucleus. In helium, the nucleus has two protons. So, we can say that the atomic number of helium is two.

Note: We could define mass number of element as the sum of atomic number and quantity of neutrons found in the nucleus. We have to know that the mass of helium is $4$. In the nucleus of helium, the number of neutrons is $2$ and the number of protons is $2$. So, when we sum up these two, we get the mass number as $4$.