Question

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

Answer 1

There are two elements in the 1^st period and eight elements in the 2^nd period., The third period starts with the element with Z = 11. Now, there are eight elements in the third period. Thus, the 3^rd period ends with the element with Z = 18 i.e., the element in the 18^th group of the third period has Z = 18. Hence, the element in the 17^th group of the third period has atomic number Z = 17.