Question

(a) Why do we classify elements?; (b) What were the two criteria used by Mendeleev in creating his Periodic Table?; (c) Why did Mendeleev leave some gaps in his Periodic Table?; (d) In Mendeleev's Periodic Table, why was there no mention of Noble gases like Helium, Neon and Argon?; (e) Would you place the two isotopes of chlorine, Cl-35 and Cl-37 in different slots because of their different atomic masses or in the same slot because their chemical properties are the same? Justify your answer.(All India - 2014)

Answer 1

Answer:

a) for a better understanding

b) formation of similiar hydrides n oxides

increasing order of atomic masses

c) for elements gallium,scandium,germanium, he predicted there would be elements

d) werent found by then

e)cause of the presence of isotopes the table was disturbed, and the modern periodic table was formed