D Block Elements

Transition elements (or transition metals) are typically defined as elements that have a partially filled subshell in their elemental state or in any of their common oxidation states. This definition usually refers to the d-block elements (Groups 3 to 12). Let's examine the elements in the options, focusing on Group 12 elements (Zn, Cd, Hg) and Group 11 elements (Cu, Ag). \begin{itemize} \item Zinc (Zn): Atomic number 30. Electronic configuration: [Ar] . In its elemental state, Zn has a completely filled subshell ( ). The most common oxidation state for Zn is +2 (Zn ). Zn electronic configuration: [Ar] (loses electrons). Since Zn has a completely filled subshell in both its elemental state and its common oxidation state, it is often not regarded as a transition element according to the strict IUPAC definition. \item Cadmium (Cd): Atomic number 48. Electronic configuration: [Kr] . Similar to Zn, Cd has a completely filled subshell ( ) in its elemental state. The most common oxidation state for Cd is +2 (Cd ). Cd electronic configuration: [Kr] . Cadmium is also not regarded as a transition element by the strict definition. \item Mercury (Hg): Atomic number 80. Electronic configuration: [Xe] . Similar to Zn and Cd, Hg has a completely filled subshell ( ) in its elemental state. Common oxidation states for Hg are +1 (as Hg ) and +2 (Hg ). Hg electronic configuration: [Xe] . Hg can be thought of as two Hg ions bonded, where Hg is [Xe] . The -shell remains full. Mercury is also not regarded as a transition element by the strict definition. \item Copper (Cu): Atomic number 29. Electronic configuration: [Ar] (exception for stability of filled -shell). Elemental Cu has . Common oxidation states are +1 (Cu ) and +2 (Cu ). Cu : [Ar] . Cu : [Ar] . Since Cu has a partially filled subshell ( ), Copper IS regarded as a transition element. \item Silver (Ag): Atomic number 47. Electronic configuration: [Kr] . Elemental Ag has . Common oxidation state is +1 (Ag ), which is [Kr] . Silver can also exist in +2 (Ag ) and +3 states in some compounds, e.g., AgO (Ag(I)Ag(III)O or Ag O depending on interpretation) or [AgF ] . Ag : [Kr] . Since Ag can form ions with a partially filled subshell (like Ag ), Silver IS regarded as a transition element. \end{itemize} The question asks which elements are NOT regarded as transition elements. Based on the definition, Zn, Cd, and Hg are the elements that have completely filled subshells ( ) in their ground state atoms as well as in their common ions. Therefore, they are often excluded from the transition elements under the strict IUPAC definition, although they are members of the d-block. Option (a) Zn, Cd, Hg lists these three elements. Option (b) Cu, Zn, Hg: Cu is a transition element. Option (c) Ag, Zn, Hg: Ag is a transition element. Option (d) Ag, Cd, Hg: Ag is a transition element. Therefore, the set of elements not regarded as transition elements is Zn, Cd, Hg.

- Ruby: Red color comes from ions doped in aluminum oxide
- Emerald: Green color due to ions in beryllium aluminum silicate
So in both gemstones, the active coloring species is

- i. Cr O is amphoteric, not acidic ⇒ incorrect
- ii. Mo and W in +6 oxidation state are more stable than Cr(VI) ⇒ correct
- iii. CuI is unstable due to disproportionation, others exist ⇒ correct
- iv. E for Cr /Cr is less positive than Mn /Mn ⇒ incorrect

CrO is basic, while Cr O is amphoteric. This statement appears correct. CrO, having chromium in a lower oxidation state (+2), exhibits more basic character. Cr O with chromium in a +3 oxidation state is amphoteric.
Nitrite is oxidized to nitrate by KMnO in acidic medium. This is a standard redox reaction.
PdCl is used as a catalyst in the Wacker process, which converts alkenes to aldehydes or ketones.
The earlier lanthanides are indeed quite reactive, similar to aluminum.
The question asks for the incorrect statement. Option (1), although seemingly true according to standard chemical properties, could be argued to be "incorrect" in a stricter sense. While CrO is basic and Cr O is amphoteric, the statement suggests a simple binary comparison. However, the basicity/acidity of oxides is also related to their oxidation states. A more accurate phrasing would compare oxides of chromium in the same oxidation state. Given that all other options are definitively correct, (1) is the most likely to be considered the incorrect statement in the context of the question.