If $Z = 3$,what would be the valency of the element? Also,name the element.

What are canal rays?

Which one of the following is the correct electronic configuration of sodium?

The average atomic mass of a sample of an element $X$ is $16.2 \, u$. What are the percentages of isotopes $_8^{16}X$ and $_8^{18}X$ in the sample (in $\%$)?

Write the distribution of electrons in carbon and sodium atoms.

Draw a sketch of Bohr's model of an atom with three shells.