20. When atoms of an element are emitting a certain wavelength (or color) of lig
ID: 692553 • Letter: 2
Question
20. When atoms of an element are emitting a certain wavelength (or color) of lig a) the atoms have gained energy and electrons have jumped to an b) the atoms have gained energy and electrons have fallen back to the ground state. c) the atoms have lost energy and electrons have fallen back to the ground state. d) the atoms have lost energy and electrons have jumped to an excited state. Use the emissions spectra results below to answer questions 21 and 22 Gas A Gas B Gas C Gas D Unknown Gas 21. According to these experimental spectra results, the unknown gas is a mixture of which gases? 22. The lines on the visible light spectrum for the gases above represent a) electrons jumping to the same excited state or energy level. b) electrons falling back down to their ground state from the same energy level. c) electrons jumping to multiple excited states or energy levels d) electrons falling back down to their ground state from multiple energy levels. 23. How do the energy and the most probable location of an electron in the third shell of an atom compare to the energy and the most probable location of an electron in the first shell of the same atom? a) In the third shell, an electron has more energy and is closer to the nucleus. b) In the third shell, an electron has more energy and is farther from the nucleus. c) In the third shell, an electron has less energy and is closer to the nucleus d) In the third shell, an electron has less energy and is farther from the nucleus. 24. An atom of oxygen is in an excited state. When an electron in this atom moves from the third shell to the second shell, energy is a) emitted by the nucleus b) absorbed by the nucleus c) emitted by the electron d) absorbed by the electron 25. Which electron configuration could represent a strontium atom in an excited state? a) 2-8-18-7-1 b) 2-8-18-8-1 c) 2-8-18-7-3 d) 2-8-18-8-2Explanation / Answer
20. When electrons fall back from a higher shell, the atom looses energy equal to the difference in energies of the two shells. That's why radiation of a 'particular' (fixed) wavelength is emitted. option C)
21. From the diagram, the spectrum of the unknown gas is clearly the overlapping of the spectrum of Gas B and Gas D.
22. Electrons may fall from any level, but as long as they return to the ground level, radiation emitted will be in the visible spectrum. option D)
23. Option B) is correct.
24. Option C) is correct.
25. The ground state electronic configuration of strontium is : 2,8,18,8,2. So, when it is excited, an electron from the penultimate shell may jump up to the valence shell. Then, configuration would be 2,8,18,7,3. option C).
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