Mass number is the number of protons and neutrons in the nucleus of an atom. And we might consider that the mass number of europium is 153 and call it good. Europium has an atomic number of 63, and there is only one stable isotope of it - europium-153. This isotope has the 63 protons and 90 neutrons. But there are other isotopes of europium, and their mass numbers range from 130 through 167 because europium has isotopes with neutron counts from 47 through 104. Use the link below for more information.
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We can find Atomic Mass and mass number in chemical elements. Atomic mass is about weight of the atom. Mass number is about total of neutrons and protons.
The atomic mass NUMBER equals the number of protons and neutrons in an atom. DO NOT confuse this with the mass of an atom.
We can find atomic mass and mass number in chemical elements. Atomic mass is about weight of the atom. Mass number is about total of neutrons and protons.
The mass number is the sum of neutrons and protons in the atomic nucleus and is different for each isotope of any element.For example the isotope oxygen-16 has the mass number 16.The mass number is not the atomic mass !!
The atomic mass number of iodine is 17.8923