Which of the following elements forms $p\pi-p\pi$ bond with itself?

$NO_2$ gas is

Thallium shows different oxidation states because

Identify the compound in which phosphorus exists in the oxidation state of $+1$.

Which of the following is a mixed anhydride?

Identify the correct orders from the following with respect to the property associated with:
$A$. $NH_3 > PH_3 > AsH_3 > SbH_3$ - Bond Angle
$B$. $NH_3 > PH_3 > AsH_3 > SbH_3$ - Basic Character
$C$. $PH_3 > AsH_3 > SbH_3 > NH_3$ - Thermal stability
$D$. $SbH_3 > NH_3 > AsH_3 > PH_3$ - Boiling point