He+211H+X Equating mass numbers on both the sides, we get 63 +1 = 1× 6 + 4 ×1+1× 2 + X = 64 -12 = 52 Equating atomic numbers on both the sides, we get 29 +1 = 6 × 0 + 2 + 2 ×1+ Y⇒Y = 30 - 4 = 26 So, the element is 26 52 Fe and iron is a d-block element, which belongs to Group 8 of the periodic table.