On the basis of Mendeleev’s Periodic Table given
below, answer the questions that follow the
(a) Name the element which is in
(b) Suggest the formula for the
(i) oxide of nitrogen
(ii) hydride of oxygen
(c) In group VIII of the Periodic Table, why
does cobalt with atomic mass 58.93 appear before nickel having
atomic mass 58.71?
(d) Besides gallium, which two other elements have since
been discovered for which Mendeleev had left gaps in his Periodic
(e) Using atomic masses of Li, Na and K, find
the average atomic mass of Li anf K and compare it wit the atomic
mass of Na. State the conclusion drawn from this activity.
(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
(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
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