Recitation Activity 6 (Chem 121)
Chapter 6
1. Consider the following 3 electronic transitions in a hydrogen atom that produce
photons of electromagnetic radiation with wavelengths depicted by waves 1-3.
a. An electron relaxing from n = 2 to n = 1 (transition A)
b. An electron relaxing from n = 4 to n = 2 (transition B)
c. An electron relaxing from n = 4 to n = 3 (transition C)
(a) Of the three electromagnetic waves shown above (1, 2 or 3) which one:
•
Has the highest frequency? 3
•
Has the highest energy? 3
•
Has the longest wavelength? 1
•
Would be emitted following transition C? 1
•
Would be emitted following transition A? 3
(b) What equation relates all 3 of the above (frequency, wavelength and energy)?
E=hν
E=hc/λ
(c) Use the Bohr model of the hydrogen atom to determine the wavelength of the photon
given off following transition B. Identify the region of the electromagnetic spectrum (IR,
Visible, UV, X-rays, etc.) that corresponds to this photon. If it is in the visible identify
the color of light.
E = -2.18 x 10-18J(1/nf2 – 1/ni2)
E=hc/λ; λ=hc/E
-18
2
2
E = -2.18 x 10 J(1/2 – 1/4 )
λ = 6.626 x 10-34Js(3.0 x 108m/s)/4.09x10-18J
E = -2.18 x 10-18J(0.1875)
λ = 4.86 x 10-7m = 486 nm
E = 4.09 x 10-18 J
VISIBLE BLUE
2. Consider the quantum numbers of all electrons in each ground state atom to answer the
following questions.
a. Which atom has more electrons with azimuthal quantum number, l = 2:
germanium (Ge) or nickel (Ni)? l=2 → which atom has more d electrons
Ge has 10 d electrons while Ni has only 8 d electrons
b. Which atom has more unpaired electrons: phosphorous (P) or chlorine (Cl)?
P: [Ne] 3s23p3 → 3 Unpaired electrons
Cl: [Ne] 3s23p5 → 1 Unpaired electron
c. Which atom has more electrons with principle quantum number, n = 3: tin (Sn) or
Krypton (Kr)?
Sn: [Ne] 3s23p64s23d104p65s24d105p2
Kr: [Ne] 3s23p64s23d104p6
Both atoms have 18 electrons with n=3
3. For each of the following “pictures” of an atomic orbital. (a) Give the common name of
the orbital type (s, p, d, f, etc.), (b) identify the azimuthal quantum number, (c) Draw
the nodal planes if any exist, (d) Give the possible values of the magnetic quantum
number.
l = 2
l = 1
ml = -2,-1,0,1,2
ml = -1,0,1
d
p
l = 0
ml = 0
s
4. Explain how Heisenberg’s Uncertainty Principle is inconsistent with the Bohr Model of
the atom. Bohr’s model places the electrons at a fixed distance from the nucleus
(so it specifies their location) and at a fixed energy (thereby specifying their
momentum). Heisenberg’s principle, when applied to electrons in an atom states
that it is inherently impossible to simultaneously know both the exact momentum of
an object and its exact location in space.
5. Use your knowledge of electron configurations to complete the crossword table. Then
unscramble the letters in the shaded boxes to spell out Niels Bohr’s native country.
A
D
E
1
C
2
3
B
4
Down
A. This element is a noble gas with exactly 18 electrons with azimuthal quantum
number, l =1.. krypton
B. A p-block element from the 5th period with 4 valence electrons. tin
C. A transition metal from the 6th period with 3 unpaired electrons. iridium
D. This transition metal element has only one electron in its 5s orbital. silver
E. An element with an [Ar] set of core electrons, two valence electrons, and 0
unpaired electrons. zinc
Across
1. A p-block element from the 5th period with 1 unpaired electron that forms diatomic
molecules in its most stable elemental form. iodine
2. This element is has more unpaired electrons that any other element in the 2nd
period. nitrogen
3. A metal from the 4th period with 4 valence electrons, and 2 unpaired electrons.
titanium
4. A member of the actinide series with 4 unpaired electrons and six valence
electrons. uranium