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Periodic Classification of Elements — Science STD 10 — Question

CBSE BoardEnglish MediumSTD 10SciencePeriodic Classification of Elements3 Marks
Question
The elements Be, Mg and Ca each having two electrons in their outermost shells are in periods 2, 3, and 4 respectively of the modern periodic table. Answer the following questions, giving justification in each case:
  1. Write the group to which these elements belong.
  2. Name the least reactive element.
  3. Name the element having largest atomic radius.
✓

Answer

Element Valence electrons Period Electronic configuration
Be
Mg
Ca
2
2
2
2
3
4
2, 2
2, 8, 2
2, 8, 8, 2
  1. All these elements belong to the $2^{\text {nd }}$ group as all have two electrons in their outermost shell.
  2. Be is the least reactive metal because reactivity of metals increases in a period as the tendency to lose electrons in a group increases.
Therefore Be being the smallest in all the given elements of a period has its valence electrons nearest to the nucleus. So the removal of electrons from its valence shell will be difficult.
  1. Ca has the largest atomic radius because it has maximum number of shells, i.e., 4.

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