Question

Mendeleev predicted the existence of certain elements not known at that time and named two of them as eka-aluminium, and eka-silicon.

(a) Name the element which has taken the place of (i) eka-aluminium, and (ii) eka-silicon
(b) Mention the period/periods of these elements in the modern periodic table.
(c) Write the group/ groups of these elements in the modern periodic table.
(d) Classify these elements as metals, non-metals or metalloids.
(e) How many valence electrons are present in the atoms of each of these elements?

Answer 1

(a) (i) Gallium is the element which has taken the place of eka-aluminium.

     (ii) Germanium is the element which has taken the place of eka-silicon.

(b) Gallium and Germanium are placed in the 4th period of the periodic table.

(c) Gallium belongs to group 13 and Germanium belongs to group 14 in the periodic table.

(d) Gallium is a metal and Germanium, a metalloid.

(e) Gallium, which belongs to group 13, has 3 valence electrons in its atom, and germanium which belongs to group 14 has 4.