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

If bromine atom is available in the form of,say,two isotopes $_{35}^{79}Br$ $(49.7 \%)$ and $_{35}^{81}Br$ $(50.3 \%),$ calculate the average atomic mass of bromine atom. (in $,u$)

Summarize the rules for writing the distribution of electrons in various shells for the first eighteen elements.

If $K$ and $L$ shells of an atom are full,then what would be the total number of electrons in the atom?

Define valency by taking examples of silicon and oxygen.

If the number of electrons in an atom is $8$ and the number of protons is also $8$,then $(i)$ what is the atomic number of the atom? and $(ii)$ what is the charge on the atom?