The atomic radium increases to the left and downwards on the periodic table.
By that logic, Se has the largest radius.
The change is that the water will freeze to 0 or minus I don’t know as I’m not to sure
You can determine this by counting the number of electrons on the last orbital. If the number of electrons on the last orbital (valence electrons) is 8 then it satisfies the octet rule because the compound has mirrored the look of a noble gass or “neutral” charge.
