# The transitional metal which form green compound in +3 oxidation state and yellow orange compound in +6 oxidation state is

$(a)\;Fe\qquad(b)\;Cr\qquad(c)\;Ni\qquad(d)\;Co$

$Cr+6K_2Cr_2O_7$-yellow
$Cr+3K_2Cr_2(SO_4)_3$-green
Hence (b) is the correct answer.