Mendeleev predicted the existence of certain elements not known at that time and named two of them as Eka-Silicon and Eka-aluminium
(a) Name the elements which have taken the place of these elements
(b) Mention the group and the period of these electron in the modern periodic table
(c) Classify these elements as metals, non-metals or metalloids
(d) How many valence electrons are present in each one of them ?

Explanation

(a) Germanium (Ge) has taken the place the Eka-silicon while gallium (Ga) has taken the place of Eka-aluminium
(b) Germanium (Ge) group 14, period 4
Gallium (Ga) group 13, period 4
(c) Gallium is other metal while germanium (Ge) is a metalloid
Note : In periodic table other metals are the metallic elements in group 13 to 16 of the periodic table. They are physically weak metals having their location between 'true metals and metalloids'
(d) Ga lies in group 13
`:.` It has `13 - 10 =3` valence electrons
Ge lies in group 14
`:.` It has `14 - 10 = 14` valence electrons.