Download CM1111* Question 1 (40 marks) Multiple Choice Questions, 5 marks

CM1111*
Question 1 (40 marks)
Multiple Choice Questions, 5 marks each. There may be more than one correct answer for
each part-question
(1) Choose the correct electronic configuration(s) from the list below:
A. The electronic configuration of Cu2+ is [Ar]4s13d9
B. The electronic configuration of O2- is [He]2s22p6
C. The electronic configuration of Cr is [Kr]4s13d5
D. The electronic configuration of Pb is [Xe]6s26p2
(2) What molecular orbital forms when the two atomic orbitals overlap in the manner
shown below:
+
A. σ
B. σ*
C. π
D. π*
(3) What is the first ionisation energy for a hydrogen atom in the ground state?
A. 0.00823 J
B. 1.63 × 10-27 J
C. 2.18 × 10-18 J
D. 7.27 × 10-36 J
(4) Which of the following statement(s) is/are true?
A. In order of increasing ionisation energy, Mg<Cs<Al<N<Si
B. Nitrogen has a lower electron affinity than oxygen
C. The 2p orbital has no radial nodes but has an angular node
D. For an s orbital, at a particular distance from the nucleus, the probability of finding the
electron is equal in all directions.
(5) Which of the following statement(s) is/are not true?
A. The node of an orbital refers to the region where its wavefunction is zero.
B. To find the energy of the electron for a Li+ ion at ground state, the energy equation for
hydrogen must be modified by multiplying with Z2 where Z=3.
C. For a hydrogen atom, the orbitals described by the quantum numbers nlm (3,1, -1) and
nlm (3, 2, -2) are degenerate.
D. The Schrodinger equation for the H2+ can be solved with exact solutions.
CM1111*
(6) State which of the following sets of quantum numbers (n, l, m) are allowed.
A. (3, 2, 3)
B. (3, 4, -1)
C. (4, 1, -1)
D. (5, 2, -2)
(7) A plot of radial distribution function R(r) against r is shown below. Which orbital can this
plot describe?
A. 3s
B. 3p
C. 5d
D. 4f
(8) Which of the following statement(s) is/are not true?
A. The angular wave function of an s orbital varies with principal quantum number n.
B. For a 4f orbital of a hydrogen atom, the maxima of the radial distribution function occurs
at 16a0, where a0 is the Bohr radius.
C. According to the Bohr model, the probability of finding an electron in a hydrogen atom
in the ground state at 0.5292 Å is 1.
D. The first ionisation energy of a He atom in the ground state is lower than the second
ionisation energy.
Question 2 (65 marks)
(1) Using Slater’s rule, determine the Zeff experienced by the 4s electrons of Ca and Ti.
(2) Give the Lewis structure of hydrazine (N2H4).
(3) Sketch the bonding picture of allene (Lewis structure given below) based on orbital
hybridization.
C C C
CM1111*
(4) Based on the molecular orbital theory in Periods 1 and 2,
(i) Which neutral homonuclear diatomic species do not exist?
(ii) Which neutral homonuclear diatomic species is/are paramagnetic?
(iii) Which neutral homonuclear diatomic species is most stable?
(4) For each of the following molecules, draw the dot-and-cross diagram and Lewis
structure(s). Based on VSEPR and VB theory, state the bond angles, number of electron
regions around the central atom, the shape of the molecule and hybridization of the central
atom.
(i) XeF2
(ii) ClO2–
(iii) NO3–
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CM1111*
Formulae and constants
e = 1.602 × 10-19 C = 4.803204 × 10-10 esu
me = 9.10938 × 10-28 g
h = 6.6261 × 10-34 J s = 6.6261 × 10-27 erg s
c = 2.99792 × 108 m s-1
RH = 1.097 × 105 cm-1
Bohr’s radius, a0 = 0.5292 Å
1 eV = 1.602 × 10-19 J
1 V = 1 J C-1
The energy levels of a hydrogen atom is given by the Bohr-de Broglie model (in cgs-esu
units):
𝐸! = −
The Rydberg formula is given by:
2𝜋 ! 𝑚! 𝑒 ! 1
, 𝑛 = 1,2,3 …
ℎ!
𝑛!
1
1
1
= 𝑅! ! − ! , 𝜆
𝑛! 𝑛!
𝑛! = 1,2,3 … ; 𝑛! = 𝑛! + 1, 𝑛! + 2, 𝑛! + 3 …