Why might spectral lines of an element in a star's spectrum be weak, even though that element is abundant in the star?
Drag the terms on the left to the appropriate blanks on the right to complete the sentences.

It is possible that an abundant element in a star does not produce strong lines, if the electrons of most of the atoms of that element ___1___ a condition to absorb light of the corresponding wavelength. For example, the Hα absorption line of hydrogen results from electrons jumping from the second to the third atomic orbital. If a star's outer atmosphere is rather cool, relatively few atoms have electrons that have absorbed enough energy to jump to the second excited state or higher; most are in the ground state. Hence, the second to third level transition occurs ___2___, and the wavelength of light corresponding to the Hα absorption line is ___3___ absorbed. A ___4___ spectral line results. If the star is very hot, then the electrons of most the hydrogen atoms may have too much energy, and may have left the atoms entirely. Such stars are mostly hydrogen, but the ionized hydrogen has no electrons to absorb light. ___5___ of hydrogen is capable of absorbing, and so the lines of hydrogen are ___6___.

WORD BANK
- strong
- are in
- most part
- frequently
- only a small part
- rarely
- are not in
- weak