Mendeleev predicted the existence of two elements and named then as Eka-silicon and Eka-aluminium.
(a) Name the elements which took over their positions at later stage.
(b) Name the groups to which these elements belong and also give their electronic configuration.
(c) Predict the valencies of these elements.
Mendeleev predicted the existence of two elements and named then as Eka-silicon and Eka-aluminium.
(a) Name the elements which took over their positions at later stage.
(b) Name the groups to which these elements belong and also give their electronic configuration.
(c) Predict the valencies of these elements.
Mendeleev's periodic table
Mendeleev arranged the elements in the increasing order of their atomic masses. He divided the elements into different groups such that the elements with similar properties are in the same group. Only 63 elements were discovered at the time of discovery of Mendeleev's periodic table. The main feature of Mendeleev's periodic table is that he left gaps between elements for the yet-to-be discovered elements and predicted their properties based on the properties of other elements in the same group. Majority of these predictions were proved with discovery of new elements. The modern periodic table is a modification of Mendeleev's periodic table.
(a) Eka-silicon and eka-Aluminium were the names given by Mendeleev for the elements that will fit the gaps he left.
Eka-silicon came after Silicon (Si) and was later discovered to be Germanium (Ge).
Eka-aluminium came after Aluminium (Al) and was later named as Gallium (Ga) after its discovery.
(b) Germanium belongs to group 14 and Gallium belongs to group 13.
Electronic configuration of Germanium is:
Ge (Atomic number- 32)- 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p2
Electronic configuration of Gallium is:
Ga (Atomic number- 31)- 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p1
(c) The valency is calculated from the number of electrons in the outer shell of the atom. If it is less than or equal to 4, valency is equal to the number of valence electrons. If the number of valence electrons is greater than 4, valency is obtained by subtracting it from 8.
Germanium contains 4 electrons in the outermost shell (4th shell). Therefore, its valency is 4. Germanium is tetravalent.
Gallium contains 3 electrons in the outermost shell (4th shell). Therefore, its valency is 3 or Gallium is trivalent.
Mendeleev's periodic table
Mendeleev arranged the elements in the increasing order of their atomic masses. He divided the elements into different groups such that the elements with similar properties are in the same group. Only 63 elements were discovered at the time of discovery of Mendeleev's periodic table. The main feature of Mendeleev's periodic table is that he left gaps between elements for the yet-to-be discovered elements and predicted their properties based on the properties of other elements in the same group. Majority of these predictions were proved with discovery of new elements. The modern periodic table is a modification of Mendeleev's periodic table.
(a) Eka-silicon and eka-Aluminium were the names given by Mendeleev for the elements that will fit the gaps he left.
Eka-silicon came after Silicon (Si) and was later discovered to be Germanium (Ge).
Eka-aluminium came after Aluminium (Al) and was later named as Gallium (Ga) after its discovery.
(b) Germanium belongs to group 14 and Gallium belongs to group 13.
Electronic configuration of Germanium is:
Ge (Atomic number- 32)- 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p2
Electronic configuration of Gallium is:
Ga (Atomic number- 31)- 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p1
(c) The valency is calculated from the number of electrons in the outer shell of the atom. If it is less than or equal to 4, valency is equal to the number of valence electrons. If the number of valence electrons is greater than 4, valency is obtained by subtracting it from 8.
Germanium contains 4 electrons in the outermost shell (4th shell). Therefore, its valency is 4. Germanium is tetravalent.
Gallium contains 3 electrons in the outermost shell (4th shell). Therefore, its valency is 3 or Gallium is trivalent.
