d and f BLOCK ELEMENTS

Why do the first ionization enthalpies of transition metals generally increase slightly across the series but show smaller variations compared to main group elements?

• Because transition metals are metals.
• Because the atomic size decreases.
• Because the nuclear charge decreases.
• Because the increasing nuclear charge is partially offset by the imperfect shielding provided by the filling d-electrons, and the ns electrons are removed first.

Why is the second ionization enthalpy of Chromium (Cr) lower than that of Vanadium (V), despite Cr having a higher atomic number?

• Because Cr is a metal.
• Because Cr has a higher atomic number.
• Because removing the first electron from Cr (4s^1) leaves it closer to the stable d^5 configuration than removing the first electron from V (4s^2) which moves it away from d^5.
• Because V has fewer electrons.

Why do the atomic radii of the second and third transition series elements not increase as much as expected compared to the first series?

• Because they are heavier.
• Because the nuclear charge increases.
• Because the Lanthanoid contraction significantly reduces the expected increase in size when moving from the second to the third series.
• Because the third series elements are less reactive.

Why do the melting points of transition metals generally peak around the middle of the series (e.g., Vanadium, Chromium, Manganese)?

• Because they are transition metals.
• Because the atomic size decreases.
• Because metals in the middle of the series typically have the optimal number of unpaired d-electrons contributing to strong metallic bonding, balancing bond strength and electron delocalization.
• Because they have high densities.

Why is the third ionization enthalpy of Vanadium (V) lower than that of Titanium (Ti), even though V has a higher atomic number?

• Because V is a metal.
• Because Ti has fewer electrons.
• Because removing the third electron from V^2+ (d^3) does not disrupt a particularly stable configuration, whereas removing the third electron from Ti^2+ (d^2) disrupts the approach towards a more stable d^3 configuration less favorably.
• Because V has a higher atomic number.