Answer:
Correc option: 
Explanation:
size of atom : it says somthing about how many shell present in a particular atom or ion and it can also be evaluated on the basis of radius of atom.
Br^- and Kr has highest number of shell as compared to other group of species .
Na ,S , Mg ,P all are from 3rd period but Kr and Br^- in the 4th period so size of species of this group will more,
Size increases on increasring the shell number
Answer: iodine 131 iodine 132 isotopes
Explanation:
The answer is C) reactants because a chemical reaction is the process in which atoms present in the starting substance rearrange to give new chemical combinations present in the substance formed by the reaction