'VALENCY' AND CHEMICAL PROPERTIES
Mendeleef drew up a table of elements considering the chemical
properties, notably the valencies, of the elements as exhibited in their
oxides and hydrides. A part of Mendeleef s table is shown in Figure
1.2 -note that he divided the elements into vertical columns called
groups and into horizontal rows called periods or series. Most of
the groups were further divided into sub-groups, for example Groups