Question

please help me guys ....i need urgent help ....answer it by solving...

Answer 1

(A) is the correct answer.. use formula_ [magnetic moment = {n(n+2)}^½ ] where 'n' is no. of unpaired electrons ,you will get a quadratic in 'n' after solving u will get two values of 'n'(i.e. 4 & –6) but negative value will be rejected as square root can't take negative values for real numbers so "n"=4. Then write electronic configuration of atom having Z=24 i.e. (Cr*) which is an exception of half filled stability i.e. 1s²2s²2p^6 3s² 3p^6 3d^5 4s¹ .. here no. of unpaired electrons are 6 {5 in 3d orbital and 1 in 4s orbital} but according to question we found the value of n=4 i.e. Cr(Z=24) must have 4 unpaired electrons, but here it is having 6 so it will lose 2 electrons to become Cr²+ to get "n"=4 .hence, value of "a" will be equal to 2.
hope it helped !