The atomic number of an element which shows the oxidation state of $+3$ is

Which of the following elements exhibits the lowest oxidation state in its compounds?

Which metals follow the stock notation method?

Which is the correct oxidation state of lead?

Using Stock notation,represent the following compounds: $HAuCl_{4}$,$Tl_{2}O$,$FeO$,$Fe_{2}O_{3}$,$CuI$,$CuO$,$MnO$,and $MnO_{2}$.

What would be the formula of the compound formed between the following elements?
$(i)$ Aluminium and Bromine
$(ii)$ Sodium and Oxygen
$(iii)$ Silicon and Oxygen
$(iv)$ Phosphorus and Chlorine