Q30 of 52 Page 43

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.

In Mendeleev’s Periodic Table, elements with similar properties can be grouped together.


Cobalt was placed in the group of rhodium (Rh) and iridium (Ir) because cobalt has properties similar to these elements.


Likewise, nickel was placed with elements such as pallidium (Pd) and platinum (Pt) because nickel has properties similar to these elements.


More from this chapter

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28

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?

 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.

 31

“Hydrogen occupies a unique position in Modern Periodic Table”. Justify the statement.

 32

Write the formulae of chlorides of Eka-silicon and Eka-aluminium, the elements predicted by Mendeleev.