Question

Of the group 18 elements, __ is the most abundant in the Earth’s crust.

Answer 1

Argon is the most abundant noble gas in the Earth’s crust. It also happens to be the most abundant noble gas in the atmosphere (0.94 $\%$ by volume). Neon is the next most abundant noble gas. In fact, these two noble gases are more abundant than better known elements like Bismuth and Arsenic.

The following table gives the abundance of group 18 elements in the atmosphere (measured as $\%$ by volume or $\%$ by moles)

$\begin{array}{cc}Noblegas& Abundance\left(\%bymoles\right)\\ He& 0.00052\\ Ne& 0.0015\\ Ar& 0.93\\ Kr& 0.00011\\ Xe& 0.0000087\\ Rn& Trace\end{array}$