Answer
$Mo,\ Cr,\ K,\ Al$
Work Step by Step
Atomic weights: $K: 39.098 u,\ Mo: 95.95 u,\ Cr: 51.996 u,\ Al: 26.982 u$
Since the mass is the same (0.10 g), the number of atoms will be inversely proportional to the atomic weights, so the samples in increasing order of the number of moles is:
$Mo,\ Cr,\ K,\ Al$
