AIIMS 2012 Chemistry Question Paper for free online practice with solutions

(a) 21Sc3+=1s2,2s22p6,3s23p6
It is colourless due to absence of unpaired electrons in d-subshell.
(b) 26Fe2+=1s2,2s22p6,3s23p63d6
It is colourless due to presence of four unpaired electrons in d-subshell.
(c) 22Ti3+=1s2,2s22p6,3s23p63d1
It is coloured due to presence of one unpaired electron in d-subshell.
(d) 25Mn2+=1s2,2s22p6,3s23p63d5
It is coloured due to 5 unpaired electrons in d-subshell.