1) Which group contains coloured ions out of 1. $Cu^{2+}$ 2. $Ti^{4+}$ 3. $Co^{2+}$ 4. $Fe^{2+}$ A) 1,2,3,4 B) 1,3,4 C) 2,3 D) 1,2 Answer: Option BExplanation:$Cu^{2+}[Ar]3d^{9}, Ti^{4+}[Ar]3d^{0} Co^{2+}[Ar]3d^{7},Fe^{2+}[Ar]3d^{6}$ 1,3,4 are coloured ions hence the answer is b.
