H05- Atomic Theory-solutions

H05- Atomic Theory-solutions - moczulski (ksm935) H05:...

Info iconThis preview shows pages 1–3. Sign up to view the full content.

View Full Document Right Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: moczulski (ksm935) H05: Atomic Theory mccord (50960) 1 This print-out should have 33 questions. Multiple-choice questions may continue on the next column or page find all choices before answering. 001 10.0 points The work function for chrominum metal is 4.37 eV. What wavelength of radiation must be used to eject electrons with a velocity of 6900 km / s? Correct answer: 8 . 88003 nm. Explanation: v = 6900 km / s = 6 . 9 10 6 m / s The wavelength of radiation needed will be the sum of the energy of the work function plus the kinetic energy of the ejected elctron. E work function = (4 . 37 eV) (1 . 6022 10- 19 J / eV) = 7 . 00161 10- 19 J E kinetic = 1 2 m v 2 = 1 2 (9 . 10939 10- 31 kg) (6 . 9 10 6 m / s) 2 = 2 . 16849 10- 17 J E total = E work function + E kinetic = 7 . 00161 10- 19 J + 2 . 16849 10- 17 J = 2 . 23851 10- 17 J Since c = , E = h = h c = h c E = 6 . 626 10- 34 m 2 kg / s 2 . 23851 10- 17 J 3 . 10 8 m / s = 8 . 88003 10- 9 m 10 9 nm 1 m = 8 . 88003 nm 002 10.0 points Which of the following provided evidence that the electrons in atoms are arranged in distinct energy levels? 1. the results of the Millikan oil-drop exper- iment 2. the existence of elements with noninteger values for atomic weights 3. the scattering of particles by a metal foil 4. the observation of line spectra from gas discharge tubes correct 5. the deflection of ions in a mass spectrom- eter Explanation: The fact that gases emitted only specific wavelengths of energy suggested that electron energy states are quantized. 003 10.0 points Assume n 1 and n 2 are two adjacent energy levels of an atom. The emission of radiation with the longest wavelength would occur for which two values of n 1 and n 2 ? 1. 2,1 2. 8,7 correct 3. 5,4 4. 4,3 5. 6,5 6. 7,6 7. 3,2 Explanation: The frequency of a photon emitted when an electron moves between levels n 1 and n 2 is given by the Rydberg equation: = R parenleftbigg 1 n 2 1- 1 n 2 2 parenrightbigg , moczulski (ksm935) H05: Atomic Theory mccord (50960) 2 where R = 3 . 29 10 15 Hz. The emission of radiation with the longest wavelength corre- sponds to that with the smallest frequency. From inspection of the formula above we see that is smallest when n 1 = 8 and n 2 = 7. Conceptual Solution : E = h = h R parenleftbigg 1 n 2 1- 1 n 2 2 parenrightbigg gives the energy of the pho- tons emitted. The emission of radiation with the longest wavelength corresponds to pho- tons with the smallest energy. From the Bohr frequency condition the energy of the emit- ted photon must be equal to the difference in energy between the higher and lower lev- els. An energy level diagram for the H-atom shows that as the energy levels get higher, the gaps between them converge; of the transi- tions listed, the two adjacent levels which are the closest together are n 1 = 8 and n 2 = 7....
View Full Document

Page1 / 9

H05- Atomic Theory-solutions - moczulski (ksm935) H05:...

This preview shows document pages 1 - 3. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online