What is the atomic number and the number of electrons in a hydrogen atom (containing $1$ proton) and a sodium atom (containing $11$ protons) respectively?

(N/A) The atomic number $(Z)$ is defined as the number of protons present in the nucleus of an atom.
For a neutral atom,the number of electrons is equal to the number of protons,which is equal to the atomic number $(Z)$.
For hydrogen: Number of protons $= 1$. Therefore,atomic number $(Z) = 1$ and number of electrons $= 1$.
For sodium: Number of protons $= 11$. Therefore,atomic number $(Z) = 11$ and number of electrons $= 11$.