Download CHM1045 - Michael Blaber

CHM1045
Fall 2000
Dr. Michael Blaber
Name_______________________________SS#_________________________
Exam #3 100 points total
Monday November 13 2000
1. A negatively charged particle is moving towards you through a magnetic field and is deflected
downward (as shown in the following diagram). Based upon the direction of deflection, and the
charge of the particle, write in the appropriate pole (i.e. "N" or "S") on the two magnets to
indicate the direction of the magnetic field (6 points)
2. Given the following frequencies for different types of electromagnetic radiation, determine
their wavelengths and indicate the general region of the electromagnetic spectrum where they
would be located (9 points)
a.  = 2.4 x 1013 s-1
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b.  = 1.5 x 1018 s-1
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c.  = 0.8 x 1016 s-1
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3. Given the following wavelengths for different types of visible light, indicate their color and
the energy contained in a single photon (10 points)
a.  = 700nm
a.  = 525nm
4. Given the following electromagnetic wave, draw a wave that has one-half the amplitude and
one-half the frequency (6 points)
5. An electron transitions from the n = 2 to the n = 4 quantum state in Bohr's model of the
hydrogen atom. Is a photon absorbed or emitted for this electron transition? (3 points). What is
the energy, frequency and wavelength of the associated photon? (9 points). Is this wavelength
visible? (3 points)
6. An electron is accelerated to 10% the speed of light. What is the characteristic wavelength of
the electron according to De Broglie's equation? (6 points)
7. What is the designation for the electron subshell with principle quantum number = 4 and
azimuthal quantum number = 3? How many orbitals are there in this subshell and how many
total electrons can it hold? (6 points)
8. Write the electron configuration for the following atoms. You may reference the nearest noble
gas electron configuration if you wish (8 points)
a) Mg
b) Cl
c) K
d) B
9. Fill in the orbital diagram for the electrons in the following atoms (9 points)
a) Be
b) O
c) P
10. For the following atoms, indicate the effective nuclear charge on the underlined valence
electrons (8 points)
a) K [Ar]4s1
b) S [Ne]3s23p4
c) C [He]2s22p2
d) Al [Ne]3s23p1
11. Answer the following questions regarding the groups of atoms or ions (9 points)
a) Which atom is larger: N, O, P, or S?
b) Which atom or ion has the higher ionization energy: Na, Mg+, K+, or Ca?
c) Which atom has the greater electron affinity (i.e. greater energy released when gaining an
electron): Be, B, C or N?
12. Given the following information for bond distances, calculate the atomic radius (not
diameter!) of for C, N, O and H atoms (8 points)
C-O 1.50Å
C-N 1.52Å
O-N 1.48Å
O-H 1.10Å
C-H 1.14Å
N-H 1.12Å
C-C 1.54Å
Radius of H:
Radius of C:
Radius of N:
Radius of O:
Constants, etc.
c (speed of light) = 3 x 108m/s
h (Planck's constant) = 6.63 x 10-34 Js
RH (Rydberg constant) = 2.18 x 10-18J
(Note: this is also known as 'B' or Bohr's constant relating electron energies in the Hydrogen
atom)
Mass of electron: 9.11 x 10-31 kg
1 Joule = 1kg m2 s-2
Note: need to memorize:
 *  = c (the relationship between wavelength, frequency and speed of light for electromagnetic
radiation)
E = h *  (the relationship between energy and frequency for electromagnetic radiation
En = -RH / n2 or En = -B / n2 (the relationship between the energy of an electron in Bohr's model
of the hydrogen atom, and the orbit number of the electron)
Elevel = RH * (1/ni2 - 1/nf2) or En = B * (1/ni2 - 1/nf2) (Energy change associated with an electron
transition from one orbit to another in the Bohr model of the hydrogen atom. Note sign on the
constant)
 = h/(mv) (DeBroglie's relationship between momentum (i.e. mass * velocity) and wavelength
for a particle.