THE PERIODIC TABLE 23
(c) sulphur,
(d) iron?
Illustrate, for each valency given, the electronic structure of a
compound in which the element displays that valency.
Discuss, as far as possible, how far the valencies chosen are in
agreement with expectations in the light of the position of these ele-
ments in the Periodic Table. (L, S)
- How, and why, do the following vary along the period sodium
to argon:
(a) the relative ease of ionisation of the element,
(b) the physical nature of the element,
(c) the action of water on the hydrides? (C, A) - A century ago, Mendeleef used his new periodic table to predict
the properties of 'ekasilicon', later identified as germanium. Some
of the predicted properties were: metallic character and high m.p.
for the element; formation of an oxide MO 2 and of a volatile
chloride MC1 4.
(a) Explain how these predictions might be justified in terms of
modern ideas about structure and valency.
(b) Give as many other 'predictions' as you can about the chemis-
try of germanium, with reasons. (Liverpool B.Sc.,Part I) - The following graph shows the variation in atomic radius with
increasing atomic number:
(^25) r
E
2
b
3
1
20
1-5
•E 10
0-5
Cu Br
10 20 30 40
Atomic number
(^5060)