Which is the last element in the series of the actinoids? Write the electronic configuration of this element. Comment on the possible oxidation state of this element.
The last element in the actinoid series is Lawrencium (Lr) with atomic number 103. Its electronic configuration is [Rn] 5f¹⁴ 7s² 7p¹.
Regarding the oxidation state, the actinoids show in general a +3 oxidation state. The elements in the first half of the series frequently exhibit higher oxidation states, but for elements in the latter half of the series (like Lawrencium), the +3 oxidation state is the most common and stable. The actinoids resemble the lanthanoids in having more compounds in the +3 state than in the +4 state.
Explanation
The question asks for the last actinoid, its electronic configuration, and oxidation state. From the NCERT curriculum, the last actinoid is Lawrencium (Lr, Z=103). The electronic configuration is [Rn] 5f¹⁴ 7s² 7p¹. The context clearly states that 'The actinoids show in general +3 oxidation state' and that 'The elements, in the first half of the series frequently exhibit higher oxidation states.' This means later elements like Lawrencium primarily exhibit the +3 oxidation state, as higher oxidation states decrease in succeeding elements.
Solution Steps
Step 1: Identify the last actinoid as Lawrencium (Lr) with atomic number 103.
Step 2: Write the electronic configuration: [Rn] 5f¹⁴ 7s² 7p¹ (5f orbitals are completely filled).
Step 3: Comment on oxidation state: Actinoids show +3 oxidation state in general; later elements like Lr primarily exhibit +3 state as higher oxidation states are more common in the first half of the series.