Which of the following elements is a metalloid?

Among the statements $(I-IV)$,the correct ones are:
$(I)$ $Be$ has smaller atomic radius compared to $Mg$.
$(II)$ $Be$ has higher ionization enthalpy than $Al$.
$(III)$ Charge/radius ratio of $Be$ is greater than that of $Al$.
$(IV)$ Both $Be$ and $Al$ form mainly covalent compounds.

Observe the following oxides. The number of amphoteric oxides from the given list is
$CO, B_2O_3, SnO_2, PbO_2, Ga_2O_3, SnO, PbO, CO_2$

Fluorine is a stronger oxidising agent than chlorine in aqueous solution. This is attributed to many factors except

Explain the classification of elements into metals,non-metals,and metalloids in the periodic table.

Identify the set of acidic oxides.