The number of amphoteric oxides from the following is
$CO_2, GeO_2, SnO_2, PbO_2, CO, GeO, SnO, PbO$

Assertion : $SiF_6^{2-}$ is known but $SiCl_6^{2-}$ is not.
Reason : Size of fluorine is small and its lone pair of electrons interacts with $d-$orbitals of $Si$ strongly.

Which ions are present in aluminosilicates?

Which one of the following elemental forms is not present in the enamel of the teeth?

Identify the element whose monoxide and dioxide are acidic in nature.

Correct statements among $(i)$ to $(iv)$ regarding silicones are:
$(i)$ they are polymers with hydrophobic character
$(ii)$ they are biocompatible
$(iii)$ in general,they have high thermal stability and low dielectric strength
$(iv)$ usually they are resistant to oxidation and used as greases.