• # question_answer 16) Write the atomic number of the element present in the third period and seventeenth group of the periodic table.

The third period starts with $3{{s}^{1}}$ and completes with$3{{p}^{6}}$. Thus, the electronic configuration of the element in question is: $[Ne]3{{s}^{2}}3{{p}^{5}}$ Therefore, the atomic number of the element is $=10+2+5=17$.