An element's mass spectrum shows exactly three peaks, at m/z 20, 21, and 22, with relative heights of 90.5%, 0.3%, and 9.2%. Which element is this?

Core Concept

Weighting the three masses gives (20)(0.905) + (21)(0.003) + (22)(0.092), which totals about 20.19 amu, matching neon's accepted average of 20.18. Three naturally occurring isotopes with a towering mass-20 peak is neon's fingerprint. Argon, potassium, and calcium show completely different peak patterns.