Question

Answer the following question:
Name the elements missing
in the Mendeleev’s periodic table with
atomic masses 44, 68 and 72. To
which group do they belong? Is there
any group for noble gases?

Answer 1

Atomic number 44- Ruthenium.
Group - 8
Period - 5
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Atomic number 68- Erbium
Group - 15
Period-6
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Atomic number 72- Hafnium
Group-4
Period - 6
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