The period of an element is determined by the value of the principal quantum number $n$ of the outermost shell. The group is determined by the valence shell electronic configuration. For (i), $n=3$ gives the 3rd period, and $ns^2 np^4$ gives Group 16. For (ii), $n=4$ gives the 4th period, and $(n-1)d^2 ns^2$ gives Group 4 of the d-block. For (iii), $n=6$ gives the 6th period, and $(n-2)f^7 (n-1)d^1 ns^2$ gives Group 3 of the f-block.