10 Group VI
(Oxygen, sulphur, selenium, tellurium, polonium)The elements in this group have six electrons in their outer quantum
level, and can thus achieve a noble gas configuration by acquiring
two electrons.PROPERTIES OF THE ELEMENTSSome of the more important physical properties of the elements are
given in Table 10.1.
Melting and boiling points increase with increasing atomic
number from oxygen to tellurium, with oxygen showing the devia-
tion typical of a group head element. The expected decrease in
ionisation energy with increase in atomic number and size of the
atoms should be noted.
Although the electron affinities do not change regularly with
increasing atomic number, the increasing ionic radii imply decreas-
ing lattice and hydration enthalpies. Hence, although oxygen forms
a large number of wholly or partly ionic oxides with metals, con-
taining O^2 ~, sulphur forms ionic compounds only with the more
electropositive elements such as sodium, and most of its compounds
are partly or wholly covalent.
All the elements are able to share two electrons forming two
covalent bonds. The two covalent bonds formed by oxygen can be
separate bonds, for example
257