Ans. No, we cannot place 16O and 18O in Mendeleev’s periodic table.
Q. Find resemblance between hydrogen and alkali metals by writing
compounds of both with chlorine, sulphur and oxygen. Ans. Alkali metals are : Li, Na, K, Rb, Cs, Fr.
Hydrogen and alkali metals form similar formulae with, oxygen, sulphur and chlorine.
Q. Find out a pair of elements from the periodic table where higher mass element is placed before lower mass element.
Ans. Co Ni ; Te I
(58.9) (58.7) (12.8) (12.7)