Q28 of 52 Page 43

Elements have been arranged in the following sequence on the basis of their increasing atomic masses.

F, Na, Mg, Al, Si, P, S, Cl, Ar, K


(a) Pick two sets of elements which have similar properties.


(b) The given sequence represents which law of classification of elements?

(i) F and Cl have similar properties. (ii) Na and K have similar properties..


(b) The given sequence represents Newland’s law of octaves. Newland’s law of octaves states that every eighth element will show similar properties as that of the first element. Therefore, above two sets will have similar properties.

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26

Which of the following set of elements is written in order of their increasing metallic character?

 27

The three elements A, B and C with similar properties have atomic masses X, Y and Z respectively. The mass of Y is approximately equal to the average mass of X and Z. What is such an arrangement of elements called as? Give one example of such a set of elements.

 29

Can the following groups of elements be classified as Dobereiner's triad ?

(a) Na, Si, Cl


(b) Be, Mg, Ca


Atomic mass of Be 9; Na 23; Mg 24; Si 28; Cl 35; Ca 40


Explain by giving reason.

 30

In Mendeleev’s Periodic Table the elements were arranged in the increasing order of their atomic masses. However, cobalt with atomic mass of 58.93 amu was placed before nickel having an atomic mass of 58.71 amu. Give reason for the same.