Q.6:- Write the atomic number of the element present in the third period and seventeenth group of the periodic table.
There are two elements in the 1st period and eight elements in the 2nd period., The third period starts with the element with Z = 11(sodium). Now, there are nine elements in the third period. Thus, the 3rd period ends with the element with Z = 18(argon) i.e., the element in the 18th group of the third period has Z = 18. Hence, the element in the 17th group of the third period has atomic number Z = 17 ,chlorine(Cl) with atomic mass 35.453, which is a p block element.