10. What is the symmetry of the following vibration (i.e. torsion of two NO₂ planes)? (A) Ag (B) B₁g (C) B₂g (D) B₃u (E) Au

1. The Nobel Prize in Chemistry in 2022 was awarded to click chemistry, or the azide-alkyne cycloaddition to connect two molecular fragments. For their initial discovery, what metal ion was required as a catalyst for this reaction to proceed at a milder condition? (A) Cu(I) (B) Zn(II) (C) Fe(II) (D) Fe(III) (E) Mo(II)