Position of Elements in the Modern Periodic Table


 
 
Concept Explanation
 

Position of Elements in the Modern Periodic Table

Position of the Elements in the Modern Periodic Table:

In order to find the position of an element in the periodic table, first write its electronic configuration then find period and group number from its electronic configuration in the following way:

  •   The period number of an element is equal to the number of electron shells in its atom. e.g. if the atom of an element has 2 electron shells (K and L), then it belongs to 2nd period.
  •     If two (or more) elements have the same number of valence shells, then they belong to the same period of the periodic table.
  •    The group number of an element having up to two valence electrons is equal to the number of valence electrons. E.g. if an element has 1 valence electron, it belongs to group 1. And if an element has 2 valence electrons, it belongs to group 2 of the periodic table. The ‘group number’ of an element having more than 2 valence electrons is equal to the number of valence electrons plus 10’. E.g. if an element has 3 valence electrons then its group number will be 3 + 10 = 13.
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    Sample Questions
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    Question : 1

    Which of the following is correct :

    (a) Ionic bond is formed when there is transfer of electrons from metal to non-metal.

    (b) Covalent bond is formed when there is sharing of electrons between two non-metals.

    (c)  Lanthanoides and actinoides are kept at the bottom of the periodic table.

    Right Option : D
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    Question : 2

    Which of the following are correct :

    (a) The period number of an element is equal to the number of electron shells in its atom.

    (b) If two (or more) elements have the same number of valence shells, then they belong to the same period of the periodic table.

    (c) If two (or more) elements have the same number of valence shells, then they belong to the different period of the periodic table.

    Right Option : A
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