Iodine is a chemical element with the symbol I and atomic number 53. The heaviest of the stable halogens, it exists as a semi-lustrous, non-metallic solid at standard conditions that melts to form a deep violet liquid at 114 degrees Celsius, and boils to a violet gas at 184 degrees Celsius.

What is Iodines atomic mass rounded?

*The standard atomic mass of iodine is 126.90447 amu, which is often rounded to 127 in simple (e.g. school textbook) versions of the Periodic Table.

What is the atomic mass of iodine 131?

126.904 is the (average) atomic mass of Iodine, and Idodine-131 is an isotope of Iodine.