Chemistry MCQs for NEET — Practice Questions with Answers

The correct electron configuration of Copper (Cu) is $ [Ar] 3d^{10} 4s^1 $. Copper also has an exceptional electron configuration where one electron from the 4s orbital is promoted to the 3d orbital to achieve a fully filled d-subshell, which is more stable. Normally, it would be $ [Ar] 3d^9 4s^2 $, but the fully filled d-orbital provides extra stability.

Cadmium (Cd) is not considered a transition element. Transition elements are defined as elements whose atoms have an incomplete d-subshell or which can give rise to cations with an incomplete d-subshell. Cadmium has a completely filled d^10 configuration in its ground state, both in its elemental form and in its common oxidation state (+2).

E°red of Ag is very high

Not all transition elements dissolve in acid. For example, some transition metals like gold (Au) and platinum (Pt) are resistant to dissolution in common acids. Transition elements are defined by their high melting points, paramagnetic properties, and various oxidation states.

The thermal stability of transition metal elements is influenced by the magnitude of their ionization enthalpy. Elements with higher ionization enthalpies tend to have more stable compounds because the energy required to remove an electron is greater, making it harder for the element to participate in reactions that would lead to decomposition.

The color of an aqueous solution of $[Ni(H_2O)_6]^{2+}$ is green. This is due to the d-d transitions of the nickel(II) ion in the octahedral crystal field created by the water ligands. The specific wavelengths of light absorbed and emitted result in the observed green color.

The complex ion $[Co(NH_3)_6]^{3+}$ is known to have a yellowish-orange color in its aqueous solution. This is due to the electronic transitions within the d-orbitals of the cobalt ion influenced by the ligand field created by the ammonia molecules.