d and f BLOCK ELEMENTS

What was Johann Dobereiner primarily known for in the context of the periodic table?

• Creating the first periodic table.
• Proposing the Law of Octaves.
• Discovering the noble gases.
• Identifying groups of three elements with similar properties and atomic weight trends.

Which property did Mendeleev *not* predict for Eka-aluminium (Gallium) based on the provided table?

• Atomic weight
• Density
• Melting point in Kelvin
• Oxide formula

What did Mendeleev leave under silicon in his table?

• Another silicon atom
• A heavier element
• A gap
• Nothing

According to Table 3.3, what was the found melting point of Gallium?

• Low
• High
• 302.93 K
• Unknown

What was a key feature of Mendeleev's classification system that set it apart?

• He only used atomic weights.
• He arranged elements alphabetically.
• He used electrical conductivity.
• He used a broader range of physical and chemical properties.