d and f BLOCK ELEMENTS

Which property of lanthanoids is most responsible for their classification as 'rare earth elements'?

• Their metallic character
• Their radioactivity
• The difficulty in separating them from their ores due to similar chemical properties
• Their scarcity in the Earth's crust

What is the primary reason lanthanoids form predominantly trivalent (Ln³⁺) ions?

• The 4f electrons are easily removed
• The 6s electrons are held very tightly
• Achieving a stable electron configuration, often a filled or half-filled f-subshell
• To resemble the alkali metals

Which lanthanoid is known for having a 5d¹ electron in its ground state configuration?

• Cerium (Ce)
• Lanthanum (La)
• Gadolinium (Gd)
• Lutetium (Lu)

What is the general electronic configuration of the outermost shell for most lanthanoid atoms?

• 5s²
• 6s²
• 7s²
• 4f¹⁻¹⁴

What is the electronic configuration of the Ac3+ ion likely to be?

• 5f 1
• 5f 2
• 5f 0
• 5f 3