To the nearest whole number, 4
380320
Take percent abundance times atomic mass for each isotope then add all up for average atomic mass.
The relative atomic mass was first proposed by John Dalton in 1803. According to it, the mass of an atom was expressed relative to the mass of one 1H atom. The unit was later changed to 1/16 of the mass of an oxygen atom. However, this measure was discarded when 17O and 18O were discovered. In 1961 the basic unit was changed (once again) to 1/12 of the mass of a 12C atom. The mass of any atom or molecule is measured in atomic mass units (AMU) and the units is defined as 1/12 the mass of a 12Carbon atom.
The atomic mass of an isotope of an element is the mass of the nucleons (neutrons + protons) in an atom of that isotope. This is nearly, though not exactly, equal to the number of nucleons, and so is nearly a whole number.The main cause for the atomic mass being fractional is that most elements have numerous isotopes, each with a different number of neutrons and so a different atomic mass. The atomic mass for an element is the average of the atomic masses of all its isotopes, weighted together in the proportion of the isotopes' abundance on earth. It is this weighting together that results in the numbers being fractional.
118.710
20.2
Aluminum's atomic mass is 26.9815386,but if rounded up,it is 27.
Zink is a meta element. Atomic mass of it is 65. Atomic number of it is 30.
Krypton is a non meta element. Atomic mass of it is 84.
Argon is a non metal element. Atomic mass of it is 39.94.
28
The atomic mass of the most stable isotope of einsteinium is 252,083 (rounded).
Nitrogen, element 7, has an atomic mass of 14.0067, rounded to 14.007.
65.41 but if rounded 65
Boron - B - Group IIIThe atomic number is 5.The mass number is 11.
15.9994amu Rounded to 16 imo
Calcium is a metal element. Atomic mass of it is 40.
The atomic mass is 201 (rounded to whole numbers). Is that what you needed?