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Periodic Classification of Elements — Science STD 10 — Question

CBSE BoardEnglish MediumSTD 10SciencePeriodic Classification of Elements5 Marks
Question
Mendeleev predicted the existence of certain elements not known at that time and named two of them as Eka-silicon and Eka-aluminium.
  1. Name the elements which have taken the place of these elements.
  2. Mention the group and the period of these elements in the Modern Periodic Table.
  3. Classify these elements as metals, non-metals or metalloids.
  4. How many valence electrons are present in each one of them?
✓

Answer

  1. Eka-silicon was later identified as Germanium (Ge) and Eka- aluminium was taken as Gallium (Ga).
  2.  
  • Germanium (Ge)- Group 14, period 4.
  • Gallium (Ga)- Group 13, period 4.
  1. Gallium(Ga) is a metal while Germanium (Ge) is a metalloid.
  2. Gallium is placed in 13th group so there must be 13 - 10 = 3 valence electrons. Similarly germanium is placed in group 14 so there must be 14 - 10 = 4 valence electrons.

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