CHEM 120R/2012
Inorganic Chemistry - Tutorial 1
School of Chemistry and Physics, University of KwaZulu-Natal, Westville Campus
Chemical Reactivity 120R
PERIODIC TRENDS & SOME ATOMIC PROPERTIES
Textbook Reference:
Brown et. al, 2nd Ed., Chapter 6
1.
Arrange the following elements in order of increasing size: K, Li, As Xe
2.
An isolated sodium atom (Na) has a radius of 186 pm. When it reacts and is
oxidized to the sodium ion (Na+) its radius size changes. Will the Na+ radius be
greater than or less than 186 pm? Explain your answer.
3.
Answer the following questions based on the graph below:
a)
Explain the change in the atomic radius
Atomic
radius, pm
between Li, Na and K (not shown), i.e. the
150
Na
Li
trend down a group of the Periodic Table.
b)
Al
Explain FULLY why there is a decrease in
100
the atomic radius of the elements in each
B
Cl
F
period from left to right.
50
10
Atomic number
4.
Arrange the elements Li, Ne, Na, and Ar in increasing order of increasing first
ionisation energy.
5.
Give two reasons why the first ionization energy (I1) of phosphorous is higher than
that of sulfur.
6.
The ionization energies for magnesium are as follows:
Ionisation
Reaction
I / kJ mol-1
I1
Mg ⇌ Mg+ + e-
736
I2
Mg+ ⇌ Mg2+ + e-
1450
I3
Mg2+ ⇌ Mg3+ + e-
7740
Explain the trend in ionisation energy from 1st to 2nd to 3rd etc.
[Hint: The electronic configuration of Mg is (Ne) 3s2]
Page 1 of 2
CHEM 120R/2012
7.
Inorganic Chemistry - Tutorial 1
For the following group of elements, select the one with the most negative electron
affinity and give at least one reason for your choice:
As, B, Cl, K, Mg, S
8.
Would you expect the elements in group 2 and group 15 (5A) to have a high or low
electron affinity? Explain your reasoning.
Page 2 of 2