Write atomic number of the element present in the third period & seventeenth group of periodic table.

Explanation

General electronic configuration of the valence shell of the elements group-17 (galogens) is `ns^(2)np^(5)`. For the third period, n=3. therefore, electronic configuration of valence shell of the element of third period and group -17 is `3s^(2)3p^(5) and` the complete. electronic configuration of this element is `1s^(2)2s^(2)2p^(6)3s^(2)3p^(5)`. therefore are total 17 electrons in this element. thus, the element to the third period and seventeenth group of the periodic table has atomic number=17.