Attempts of Elements Classification | summary

The video tutorial summarizes the evolution of element classification, starting with Mendeleev's periodic table, which arranged elements by atomic weights and properties, but had limitations due to isotopes. Mosely later discovered that atomic numbers, not weights, determine periodicity, leading to the modern periodic table with elements arranged by atomic numbers in groups and periods, including inert gases and lanthanides/actinides.

Who was the first scientist to create a real periodic table?

• Dmitri Mendeleyev

• John Dalton

• Marie Curie

• Henry Mosely

What was a major limitation of Mendeleyev's periodic table?

• It had no gaps for new elements.

• It did not account for isotopes.

• It was based on atomic numbers.

• It included inert gases.

What did Mosely discover about the periodicity of elements?

• It is related to electron configurations.

• It is related to chemical properties.

• It is related to atomic weights.

• It is related to atomic numbers.

Which group did Mosely add to the periodic table?

• Alkali metals

• Inert gases

• Halogens

• Transition metals

How are elements arranged in the modern periodic table?

• By atomic numbers

• By atomic weights

• By physical properties

• By chemical properties