What are canal rays?

Define valency by taking examples of silicon and oxygen.

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

What are the limitations of Rutherford's model of the atom?

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 $,u$)

$Na^{+}$ has completely filled $K$ and $L$ shells. Explain.