D And F Block Elements

we need to examine the electron configurations of the elements.
(A) Sm (Z=61) has the electronic configuration: [Xe] 4f⁶ 6s² Eu (Z=63) has the electronic configuration: [Xe] 4f⁷ 6s²
In both cases, the 5d-subshell is not yet occupied, so this pair does not fulfill the given condition.
(B) Gd (Z=64) has the electronic configuration: [Xe] 4f⁷ 5d¹ 6s² Lu (Z=71) has the electronic configuration: [Xe] 4f¹⁴ 5d¹ 6s²
In this pair, both Gd and Lu have one electron in the 5d-subshell, satisfying the condition.
(C) Ce (Z=58) has the electronic configuration: [Xe] 4f¹ 5d¹ 6s² Nd (Z=60) has the electronic configuration: [Xe] 4f⁴ 5d⁰ 6s²
In this pair, only Ce has one electron in the 5d-subshell, so it satisfies the condition.
(D) Lu (Z=57) has the electronic configuration: [Xe] 4f¹⁴ 5d¹ 6s² Dy (Z=66) has the electronic configuration: [Xe] 4f¹⁰ 5d⁰ 6s²
In this pair, only Lu has one electron in the 5d-subshell, so it satisfies the condition.
Therefore, the correct pair of elements is: (B) Gd (Z=64) and Lu (Z=71)

The highest oxidation state of manganese is +7.
Manganese is a transition metal that can exhibit various oxidation states ranging from -3 to +7. The most common oxidation states of manganese are +2, +3, +4, +6, and +7. However, the +7 oxidation state is the highest oxidation state observed for manganese in chemical compounds.
An example of a compound in which manganese exhibits the +7 oxidation state is potassium permanganate (KMnO₄).

The element Eu refers to Europium, which is an inner transition element.

Inner transition elements: These elements are part of the f-block of the periodic table, which consists of two rows of elements known as the lanthanides and actinides. The lanthanides and actinides are collectively referred to as the inner transition metals because their electron configuration involves the filling of f-orbitals.

Europium (Eu): Europium is a member of the lanthanide series, which is the first row of inner transition elements. The lanthanides are characterized by the filling of the 4f subshell with electrons. Europium has the atomic number 63 and the electron configuration [Xe] 4f⁷ 6s². Europium is known for its unique properties, such as being one of the few elements that can be trivalent (Eu³⁺) and divalent (Eu²⁺).

Properties of Europium:

• Color: Europium compounds are often brightly colored and are widely used in phosphorescent and fluorescent applications, such as in red phosphors for color television tubes and computer screens.
• Magnetic properties: Europium is known for its strong magnetic properties, particularly in the Eu²⁺ state.
• Occurrence: Europium is relatively rare in nature but is extracted from minerals like monazite and bastnäsite, which contain other lanthanides as well.

Lanthanide Series (Inner Transition Elements): The lanthanide series consists of 15 elements, from Lanthanum (La, atomic number 57) to Lutetium (Lu, atomic number 71). These elements have similar chemical properties due to the filling of their 4f orbitals. Europium (Eu) is one of these elements, and its unique electronic configuration allows it to have special applications in lighting and as a reagent in chemical analysis.

Conclusion: Europium (Eu) is an inner transition element because it belongs to the lanthanide series, where elements fill the 4f orbitals. It is used extensively in various high-tech and luminescent applications due to its electronic properties.