Helium was discovered by

Match the Xenon compounds in Column-$I$ with their structures in Column-$II$ and assign the correct code.

Column-$I$	Column-$II$
$(a) XeF_{4}$	$(i) \text{Pyramidal}$
$(b) XeF_{6}$	$(ii) \text{Square planar}$
$(c) XeOF_{4}$	$(iii) \text{Distorted octahedral}$
$(d) XeO_{3}$	$(iv) \text{Square pyramidal}$

Code: $(a) \quad (b) \quad (c) \quad (d)$

Assertion $(A)$: The boiling points of noble gases increase from $He$ to $Xe$.
Reason $(R)$: The interatomic van der Waals' attractive forces increase from $He$ to $Xe$.
The correct answer is:

Which noble gas is the most abundant in the atmosphere?

Which of the following is not correct for the given reaction sequence:
$XeF_6 + H_2O \rightarrow A + 2HF$
$XeOF_4 + H_2O \rightarrow B + 2HF$
$XeO_2F_2 + H_2O \rightarrow C + 2HF$

$XeO_4$ molecule is tetrahedral having