Question

(i) What were the criteria used by Mendeleev in creating his Periodic Table?
(ii) Why do you think the noble gases are placed in a separate group?
(iii) By considering their position in the Periodic Table, which one of the following elements would you expect to
have maximum metallic characteristics?
Ga Ge As Se Be
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Answer 1

Answer:

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Answer 2

Answer:

(1) Mendeleev used atomic mass of the elements as the unique criteria of the elements. He proposed that the chemical properties of elements are the periodic function of their atomic masses. And thus, he arranged the elements in the increasing order of their atomic masses.

(2) Halogens are extremely reactive elements because they need one more electron to gain a full octet state while noble gases are extremely unstable because they already have their full octet state, hence they are placed in separate groups of the periodic table.

(3) Be and Ga are expected to be most metallic. Out of Be and Ga, Ga is bigger in size and hence has greater tendency to lose electrons than Be.