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- Some elements have more than one stable (nonradioactive) isotope —variants of the same substance, but with different numbers of neutrons in their atomic nuclei that alter the mass. (The element's identity is determined by the number of protons.)
www.scientificamerican.com/article/mass-migration-chemists/Mass Migration: Chemists Revise Atomic Weights of 10 Elements
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Why does atomic mass change with atomic weight?
Does increasing the number of protons increase atomic mass?
Does increasing atomic number equate to increasing mass?
Why do atoms have different mass numbers?
Why does atomic mass increase from left to right?
How do atomic masses increase in a periodic table?
Jul 1, 2019 · The atomic weight can change because it depends on our understanding of how much of each isotope of an element exists. Both atomic mass and atomic weight rely on the atomic mass unit (amu), which is 1/12th the mass of an atom of carbon-12 in its ground state.
- Anne Marie Helmenstine, Ph.D.
Jan 9, 2018 · The reason increasing atomic number doesn't always equate to increasing mass is because many atoms don't have the same number of neutrons and protons. In other words, several isotopes of an element may exist.
- Anne Marie Helmenstine, Ph.D.
Feb 13, 2014 · Atomic masses increase from left to right and from top to bottom of the Periodic Table. Explanation: As you go from left to right in the Periodic Table, you are adding more protons and neutrons to the nuclei.
The relative masses of atoms are reported using the atomic mass unit (amu), which is defined as one-twelfth of the mass of one atom of carbon-12, with 6 protons, 6 neutrons, and 6 electrons. The atomic mass of an element is the weighted average of the masses of the naturally occurring isotopes.
Jan 30, 2023 · A different mass size is due to the difference in the number of neutrons that an atom contains. Although mass numbers are whole numbers, the actual masses of individual atoms are never whole numbers (except for carbon-12, by definition). This explains how lithium can have an atomic mass of 6.941 Da.
The atomic mass of atoms, ions, or atomic nuclei is slightly less than the sum of the masses of their constituent protons, neutrons, and electrons, due to binding energy mass loss (per E = mc2).
Jun 26, 2023 · Define atomic and mass numbers. Determine the number of protons, neutrons, and electrons in an atom. Identify the charge and relative mass of subatomic particles.
