Which group of elements could be placed in Mendeleev's Periodic Table

1.	Which group of elements could be placed in Mendeleev's Periodic Table without disturbing the original order? Give reason
Answer» Inert gases (Noble gases) could be placed in Mendeleev’s Periodic Table without disturbing the original order. Before Mendeleev Noble gases; like Helium. Neon and Argon had been mentioned by various scientists. But these gases could be grouped together as noble gases much later than Mendeleev’s discovery. Mendeleev used 63 elements till his periodic table because these were the only known elements till his time. However, he was bold enough to leave gaps in his periodic table. He had predicted that that more elements would be discovered in times to come. Mendeleev’s Periodic Table was the first comprehensive attempt to classify elements on the basis of their chemical properties. This is the main reason that new elements could be easily placed in Mendeleev’s Periodic Table without disturbing the original order.

Which group of elements could be placed in Mendeleev's Periodic Table without disturbing the original order? Give reason

Answer»

Inert gases (Noble gases) could be placed in Mendeleev’s Periodic Table without disturbing the original order.

Before Mendeleev Noble gases; like Helium. Neon and Argon had been mentioned by various scientists.
But these gases could be grouped together as noble gases much later than Mendeleev’s discovery.
Mendeleev used 63 elements till his periodic table because these were the only known elements till his time.
However, he was bold enough to leave gaps in his periodic table.
He had predicted that that more elements would be discovered in times to come.
Mendeleev’s Periodic Table was the first comprehensive attempt to classify elements on the basis of their chemical properties.

This is the main reason that new elements could be easily placed in Mendeleev’s Periodic Table without disturbing the original order.