# Tutorial: Atom and Electron Affinity

Topics: Atom, Quantum mechanics, Atomic orbital Pages: 3 (891 words) Published: September 15, 2013
DIVISION OF CHEMISTRY :MODULE: GENERAL CHEMISTRY (CHY2021) TUTORIAL # 2

DATE: September 2013

1. Define the following terms: mass number, atomic number and the atomic mass unit (amu). 2. With the help of The Periodic Table, complete the table below. Symbol Atomic # Proton # Neutron # # of Electrons Mass Number Charge Ar 19 31 17 18 35 20 18 3+ 40

3. In your own words, explain Thomson’s and Rutherford’s contribution to the atomic theory. Give sketches to substantiate your answer. 4. Explain how Bohr contributed in defining the structure of the atom. 5. Magnetic resonance imaging (MRI) is a powerful diagnostic tool used in medicine. The imagers used in hospitals operate at a frequency of 400 MHz (1 MHz = 106 Hz). Calculate: (a) The wavelength (b) The energy in J per photon (c) The energy in kJ per mol 6. Calculate the energies of the following waves (in kilojoules per mole), and tell which number of each pair has the higher value. (a) An FM radio wave at 99.5 MHz and an AM radio wave at 1150 KHz (b) An X ray with λ = 3.44 x 10-9 m and a microwave with λ = 6.71 x 10-2 m 7. What is the wavelength (in meters) of photons with the following energies? (a) 90.5 kJ/mol (b) 8.05 x 10-4 kJ/mol (c) 1.83 x 103 kJ/mol 8. Protons and electrons can be given very high energies in particle accelerators. What is the de Broglie wavelength (in meters) of an electron (mass = 9.109 x 10-31 kg) that has been accelerated to 99% of the speed of light? 9. What is the de Broglie wavelength (in meters) of the baseball weighing 145g and travelling at 156km/h? 10. Calculate : (a) The energy difference from the transition that result when an electron drops from the fourth orbit to the second in a hydrogen atom. (b) The energy of the n = 4 level. (c) the wavelength in metres (m) of the spectral line. (d) Is energy absorbed or released during this transition?

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11. An electron falls to the n= 1 energy level (i.e. nf =1) during a transition. The wavelength of the line emitted was 95...