d and f BLOCK ELEMENTS

What is a significant reason for the greater variability in oxidation states observed in Actinoids compared to Lanthanoids?

• Actinoids have more electrons.
• Actinoids are radioactive.
• The 5f, 6d, and 7s orbital energies are more similar in Actinoids than the 4f, 5d, and 6s orbital energies are in Lanthanoids.
• Actinoids are heavier.

What is the most common oxidation state for Uranium (U)?

• +3
• +4
• +5
• +6

What is the most common oxidation state for Thorium (Th)?

• +2
• +3
• +4
• +5

What is the most common oxidation state for Actinium (Ac)?

• +2
• +3
• +4
• +5

Why is the +2 oxidation state particularly stable for Europium (Eu) and Ytterbium (Yb)?

• Because they have fewer protons.
• Because they are lighter elements.
• Because Eu2+ has a half-filled f-subshell (4f7) and Yb2+ has a fully-filled f-subshell (4f14).
• Because they are radioactive.