Question

The emission spectrums are known for the elements below.

Line spectra for boron, lithium, hydrogen, helium, potassium and unknown sample. Boron has 3 purple lines, 1 blue line, 2 blue-green lines and 2 orange lines. Lithium has 2 purple lines, 2 blue lines, 2 blue-green lines, 1 orange line and 1 red line. hydrogen has one line of each purple, blue, blue-green and red. helium has 3 purple lines, 3 blue lines, 3 blue-green lines 1 yellow line and 2 red lines. Potassium has 8 purple lines, 6 blue-green lines, 10 green lines, 3 yellow lines, 2 orange lines and 6 red lines. The unknown sample has Potassium has 8 purple lines, 6 blue-green lines, 10 green lines, 3 yellow lines, 2 orange lines and 6 red lines.

What elements are in the unknown sample? Select 2 options.

boron
lithium
hydrogen
helium
potassium

Answer 1

I can't find a pair that matches the unknown spectrum exactly.

Reasoning:
- The unknown shows green lines. Of the given elements only potassium produces green lines, so potassium must be present.
- Every other listed element (B, Li, H, He) produces blue lines, but the unknown spectrum has no blue lines. Adding any of those to potassium would introduce blue lines (or increase counts in colors that the unknown doesn't have), so none of them can be present in addition to potassium if the unknown spectrum is exactly as stated.
- No pair of the non-potassium elements sums to potassium's counts.

Conclusion:
- The unknown sample is potassium (only). If the question truly requires selecting two elements, the problem statement or the unknown spectrum contains an error — please double-check the data and confirm whether you meant to ask for one element or to give a different unknown spectrum.