Q6 of 56 Page 1

Choose from the following:

20Ca, 3Li, 11Na, 10Ne.


(i) An element having two shells completely filled with electrons.


(ii) Two elements belonging to the same group of the periodic table.










(i) The electronic configuration of following compounds will be:


Ca: 2,8,8,2


Li: 2,1


Na: 2,8,1


Ne: 2,8


So, the element having two shells completely filled is Neon I.e. Ne.


(ii) The elements belong to the same group if they have same number of valence electrons. Since Li and Na have same number of valence electrons, so they belong to the same group.


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(a) Which two criteria did Mendeleev use to classify the elements in his periodic table?

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