Answer:
Einsteinium is heavier
Explanation:
Atomic weight is what we are referring to when figuring out how heavy an element is and is measured in amu (atomic mass units)
(This is also the same as the molar mass how heavy 6.022 x 10^23 atoms of a substance or element is which is measured in grams)
The atomic weight of an element can be found on a periodic table.
Europium has an atomic mass of approximately 152 amu (atomic mass units)
Einsteinium has an atomic mass of approximately 252 amu.
Einsteinium has a higher atomic weight so it's heavier.
There's another easier way of going about it where you don't even have to think about the actual number and basically just look at the element's atomic number and position on the periodic table.
Eu is 63
Es is 99
As the atomic number increases on the periodic table this means it's number of protons is greater.
Protons lie in the nucleus which has most of the atom's weight so the more protons the heavier it is.
Einsteinium has a higher atomic number meaning it has more protons so we can assume it's the heavier one.
Hope this helps!
