Write the Bohr Bury scheme to fill the electrons in various energy levels of an atom.

Using these rules, write the electron arrangement of the elements having atomic numbers $11$ and $18$.

What is mass number of an element? How is the mass number related to the protons and neutrons present in the nucleus of an atom? Is it same as atomic number?

Write electronic configuration for the following element:

${}_8{}^{16}\mathrm{O}$

Write electronic configuration for the following element:

${}_{14}{}^{28}\mathrm{Si}$

Write electronic configuration for the following element:

${}_{18}{}^{40}\mathrm{Ar}$

Name the element which has the following electronic configuration:

$2, 6$