question_answer 70)

    Mendeleev predicted the existence of certain elements not known at that time and named two or 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, nonmetals or metalloids. (d) How many valence electrons are present in each one of them?

Answer:

                (a) Germanium (Ge) has taken the place of 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.                 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=4 valence electrons.