d and f BLOCK ELEMENTS

What is the primary reason Cr2+ (d4) is a better reducing agent than V2+ (d3), according to principles discussed in the text?

• Cr2+ has a higher charge.
• V2+ is more stable than Cr2+.
• Cr2+ has a lower atomic number.
• Cr2+ achieves greater stability by losing an electron to reach the d3 configuration with a half-filled t2g level, compared to V2+ which is already relatively stable.

Why is the E°(M2+/M) value for Zn more negative than expected from the simple trend according to the text?

• Its low atomic mass.
• Its high ionization enthalpy.
• Its low hydration enthalpy.
• Because the formation of the stable, fully filled d10 electronic configuration in Zn2+ provides extra stability not fully captured by basic thermochemical calculations.

If a metal's calculated E°(M2+/M) value is less negative than its observed value, what might this imply according to the context provided by the text?

• The calculation is perfectly accurate.
• The calculation overestimates the energy cost.
• The calculation overestimates the energy gain.
• The calculation might underestimate the stability gained by forming the M2+ ion due to specific electronic configurations.

What is the main factor determining the general trend of E°(M2+/M) values becoming less negative across the first transition series, according to the text?

• The general decrease in atomization enthalpy.
• The general increase in hydration enthalpy.
• The stability of half-filled d orbitals.
• The general increase in the sum of the first and second ionization enthalpies.

Why is the d5 electronic configuration significant in the context of Mn chemistry, according to the text?

• It makes Mn2+ highly reactive and unstable.
• It makes Mn3+ a strong reducing agent.
• It has no significant impact on Mn's redox behavior.
• It provides extra stability to the Mn2+ ion, making Mn3+ a strong oxidizing agent.