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) for Eka-silicon and gallium (Ga) for Eka-aluminium
(b) Germanium (Group 14 and Period 4)
Gallium (Group 13 and Period 4)
(c) Germanium (Metalloid), Gallium (Metal)
(d) Germanium (Z = 32), Four valence electrons (2, 8, 18, 4)
Gallium (Z = 31) , Three valence electrons (2, 8, 18, 3).