There are 14 elements in actinoid series. Which of the following elements does not belong to this series?

Which of the following reactions are disproportionation reactions?

(a) Cu+ → Cu²⁺ + Cu

(b) 3MnO₄^2– + 4H⁺→ 2MnO₄^– + MnO₂ + 2H₂O

(c) 2KMnO₄→ K₂MnO₄ + MnO₂ + O₂

(d) 2MnO₄^– + 3Mn²⁺ + 2H₂O → 5MnO₂ + 4H⁺

When KMnO₄ solution is added to oxalic acid solution, the decolourisation is slow in the beginning but becomes instantaneous after some time because

KMnO₄ acts as an oxidising agent in acidic medium. The number of moles of KMnO₄ that will be needed to react with one mole of sulphide ions in acidic solution is

Gadolinium belongs to 4f series. It’s atomic number is 64. Which of the following is the correct electronic configuration of gadolinium?