d and f BLOCK ELEMENTS

Which of the following 3d transition metal ions would you expect to be most likely diamagnetic in an octahedral complex with weak field ligands?

• Ti^2+
• Cr^3+
• Zn^2+
• Mn^2+

What is the ground state electronic configuration of Copper (Cu, Z=29), and why is it an exception to the expected Aufbau principle?

• [Ar] 3d^9 4s^2; It follows the Aufbau principle.
• [Ar] 3d^11; It has an extra electron in the d-subshell.
• [Ar] 3d^10 4s^1; A completely filled 3d subshell (d^10) is more stable than the expected [Ar] 3d^9 4s^2 configuration.
• [Ar] 4s^2 4p^7; It fills the p-orbital instead.

What is the ground state electronic configuration of Chromium (Cr, Z=24), and why is it an exception to the expected Aufbau principle?

• [Ar] 3d^4 4s^2; It follows the Aufbau principle.
• [Ar] 3d^6; It has a filled 3d subshell.
• [Ar] 3d^5 4s^1; A half-filled 3d subshell (d^5) is more stable than the expected [Ar] 3d^4 4s^2 configuration.
• [Ar] 4s^2 4p^4; It fills the p-orbital instead.

Why is the third ionization enthalpy of transition metals not necessarily highest for the element with the most protons in the first transition series?

• Because atomic size decreases across the series.
• Because ionization enthalpies depend significantly on the stability of the electronic configuration of the ion formed, particularly half-filled or fully filled subshells.
• Because all transition metals have similar properties.
• Because the first transition series elements are metals.

What can be inferred about the magnetic moment of K2[MnCl4] having a value of 5.9 BM?

• It indicates one unpaired electron, a low-spin configuration.
• It indicates five unpaired electrons, confirming the high-spin d^5 configuration for Mn(II) in a tetrahedral field.
• It indicates three unpaired electrons.
• It indicates the complex is diamagnetic.