Atomic number of Cr and Fe are respectively 24 and 26 , which of the following is paramagnetic?

Step-by-step solution

Odd electrons, ions and molecules are paramagnetic. In ( Cr ( CO )₆ ) molecule 12 electrons are contributed by CO group and it contains no odd electron. ( Cr 3 d^5 4 s^1 ) ( Fe ( CO )₅ ) molecule also does not contain odd electron. ( aligned & Fe 3 d^6 4 s^2 & In [ Fe ( CN )₆ ]^4 ion Fe (+ II ) 3 d^6 4 s^0 aligned ) ( ) No odd electrons. ( In [ Cr ( NH ₃ )₆ ]³⁺ ion Cr (+ III ) 3 d^3 4 s^0 ) This ion contains odd electron so it is paramagnetic.