What is the Difference Between Atomic Weight and Mass Number?
🆚 Go to Comparative Table 🆚The difference between atomic weight and mass number lies in their definitions and how they are determined:
- Atomic Weight: This is the average mass of all the isotopes of a certain type of element. It is measured in units of atomic mass (usually abbreviated to AMU), also known as Daltons. A single element can have several isotopes, and the atomic weight is dependent on the atomic masses of these isotopes and their abundance.
- Mass Number: This is the number of protons and neutrons in an atom. It tells us about the mass of the atom in atomic mass units (AMU). The mass number is a whole number value and is independent of the atomic masses of isotopes.
In summary:
- Atomic weight is the average mass of all isotopes of an element, dependent on the atomic masses of isotopes and their abundance.
- Mass number is the total number of protons and neutrons in an atom, determining the mass of the atom in atomic mass units.
On this pageWhat is the Difference Between Atomic Weight and Mass Number? Comparative Table: Atomic Weight vs Mass Number
Comparative Table: Atomic Weight vs Mass Number
The key difference between atomic weight and mass number lies in the fact that atomic weight is the average mass calculated considering all the isotopes of an element, while mass number represents the total number of nucleons in the atom's nucleus. Here is a table highlighting the differences between atomic weight and mass number:
| Property | Atomic Weight | Mass Number |
|---|---|---|
| Definition | Atomic weight is the average mass of an element, considering all its isotopes. | Mass number is the total number of nucleons (protons and neutrons) in the atom's nucleus. |
| Calculation | Atomic weight is calculated by considering the relative abundances of isotopes and their respective atomic masses. | Mass number is determined by counting the number of protons and neutrons in the atom's nucleus. |
| Relation to Isotopes | Atomic weight takes into account the average mass of all isotopes present in an element in different percentages. | Mass number is specific to individual isotopes. |
| Unit of Measurement | Atomic weight is usually expressed in unified atomic mass units (u or amu). | Mass number is typically expressed as a whole number, corresponding to the total number of nucleons in the atom's nucleus. |
In summary, atomic weight represents the average mass of an element considering all its isotopes, while mass number indicates the total number of nucleons in the atom's nucleus.
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