Download science 1 small-group tutorial scheme

Assignment No.2
Introduction to Chemistry
Tutorial Scheme 2001/2002
CM1003/CM1005 Introduction to Chemistry
Answers to the following problems should be placed in your tutor's box situated
outside Room 225 in the Robert Kane Building by 5 pm Friday 1nd November 2002.
1. (a)
(b)
What is an isotope?
Indicate the number of protons, neutrons and electrons in:
(i)
(c)
7
Li
3
(ii)
11
B
5
(iii)
31
P
15
(iv)
56
Fe
26
Calculate the weighted average atomic mass of naturally occurring tungsten, given that the element
contains five isotopes:
180
W
74
2. (a)
184
(0.14%), 182
W (26.41%), 183
W (14.40%),
W (30.64%) and 186
W (28.41%).
74
74
74
74
Describe in simple terms the molecular and atomic processes which are involved in the hydrogen
emission spectrum experiment.
(b)
The hydrogen emission spectrum experiment gives rise to a line spectrum. What does this tell us
about the electromagnetic radiation being given out by the hydrogen atom? How was this result
explained in terms of the simple Quantum Mechanical (Bohr) model of atomic structure?
(c)
Given that the Rydberg constant has the value 1.1 x 10-2 nm-1, calculate the wavelength of the first
line in the Lyman series (n=1) in the hydrogen emission spectrum.
3. (a)
List all the subshells and orbitals for which the principal quantum number, n, has the values 2 and 3
in order of increasing energy, according to the quantum mechanical rules. Use clearly-labelled
diagrams to illustrate the shapes and orientations of the orbitals for which the angular momentum
(subsidiary, azimuthal) quantum numbers  is equal to 0, 1 and 2.
(b) Use the so-called 'diagonal diagram' to derive the full electronic configurations for the elements of Z
= 5, 17 and 24. Comment on the significance of the configuration adopted by the last of these
elements.
4 (a) What is the Effective Nuclear Charge of the following atoms?
H, C, Ne, Ca, Cs, I
(b) Which of the following pairs of atoms has the larger radius?
Na and K , Rb and Sn, Li and Br, O and S
(c) Which of the previous pairs of atoms has the larger ionisation energy? Why?