Choose the correct order of acidic strength for $CO_2, CuO, CaO, H_2O$.

Which of the following is $Not$ predominantly acidic or amphoteric oxide?

Which of the following oxides is different from the other three oxides?

Which of the following oxides is most amphoteric?

Why do elements in the same group have similar physical and chemical properties?

The first $\left( \Delta_{i}H_{1} \right)$ and the second $\left( \Delta_{i}H_{2} \right)$ ionization enthalpies (in $kJ \ mol^{-1}$) and the $\left( \Delta_{eg}H \right)$ electron gain enthalpy (in $kJ \ mol^{-1}$) of a few elements are given below:

Elements	$\left( \Delta_{i}H_{1} \right)$	$\left( \Delta_{i}H_{2} \right)$	$\left( \Delta_{eg}H \right)$
$I$	$520$	$7300$	$-60$
$II$	$419$	$3051$	$-48$
$III$	$1681$	$3374$	$-328$
$IV$	$1008$	$1846$	$-295$
$V$	$2372$	$8581$	$+48$
$VI$	$738$	$1451$	$-40$

Which of the above elements is likely to be:
$(a)$ the least reactive element.
$(b)$ the most reactive metal.
$(c)$ the most reactive non-metal.
$(d)$ the least reactive non-metal.
$(e)$ the metal which can form a stable binary halide of the formula $MX_{2}$ ($X =$ halogen).
$(f)$ the metal which can form a predominantly stable covalent halide of the formula $MX$ ($X =$ halogen)?