For elements with no stable isotopes (like Ununoctium), the mass number of the isotope with the longest half-life is used. That's 294.
Ununoctium.
The element Ununoctium, Uuo, has an atomic mass of 293.
The relative atomic mass of ununoctium is estimated as 294.
Ununseptium and Ununoctium are currently tied.
Ununseptium and Ununoctium are currently tied.
Ununoctium, with the chemical symbol Uuo, has the atomic number 118.
The estimated atomic radius of ununoctium is 152 pm.
The isotope ununoctium-294 has 118 protons and electrons and 176 neutrons.
The average atomic mass for titanium is 47.867.
The average atomic mass of Lithium (Li) is 6.941.
Radon, unless you count the synthetic Ununoctium. But because it is radioactive, highly unstable, and synthetic, I would discount it for now. It does however have the largest atomic mass for any known atomic substance. So, the answer is Radon.
The average atomic mass is a weighted average of the masses of all isotopes of an element, taking into account their abundance. The atomic mass listed on the periodic table is the weighted average of all naturally occurring isotopes of the element. So, they are essentially the same thing, with the average atomic mass being a more specific term.