What is the difference between atomic mass and atomic weight?
Atomic mass is the mass of an individual atom, whereas atomic weight is the average (weighted) of the atomic masses of an atom’s naturally occurring isotopes.
Atomic mass is characterized by the number of protons in the nucleus, whereas atomic weight is the average (weighted) of the atomic masses of an atom’s naturally occurring isotopes.
Atomic mass is the average of the atomic masses of an atom’s naturally occurring isotopes, whereas atomic weight is the weight of an individual atom.
Atomic mass is characterized by the number of neutrons in the nucleus, whereas atomic weight is the weight of an individual atom.
Atomic weight – Atomic mass x g.
The correct answer and explanation is :
The correct answer is: Atomic mass is the mass of an individual atom, whereas atomic weight is the average (weighted) of the atomic masses of an atom’s naturally occurring isotopes.
Explanation:
The terms atomic mass and atomic weight are often used interchangeably, but they refer to different concepts, and understanding their distinction is important in chemistry and physics.
- Atomic Mass:
- Atomic mass refers to the mass of a single atom of a given isotope. It is typically expressed in unified atomic mass units (amu) or Daltons (Da).
- The atomic mass of an atom is determined by the total number of protons and neutrons in its nucleus. Electrons contribute negligibly to the mass of an atom because their mass is much smaller than that of protons or neutrons.
- For example, the atomic mass of a carbon-12 (¹²C) atom is exactly 12 amu, as it contains 6 protons and 6 neutrons. Similarly, isotopes of carbon, like carbon-14 (¹⁴C), have different atomic masses because they contain a different number of neutrons.
- Atomic Weight:
- Atomic weight (also known as relative atomic mass) is a weighted average mass of the naturally occurring isotopes of an element, taking into account their relative abundances. It is a dimensionless number, although it is typically expressed in atomic mass units (amu) on the periodic table.
- Since most elements have more than one naturally occurring isotope, their atomic weight is calculated as the average of the atomic masses of all their isotopes, weighted by how abundant each isotope is in nature. For example, the atomic weight of carbon is approximately 12.01 amu, which reflects the presence of both carbon-12 and carbon-14 in nature, with carbon-12 being much more abundant.
Key Differences:
- Atomic Mass refers to a single atom of a specific isotope, whereas atomic weight reflects the average mass of all naturally occurring isotopes of an element.
- Atomic mass is specific to individual atoms, while atomic weight considers isotopic distribution and natural abundance.
To sum up, atomic mass is for individual atoms, and atomic weight is an average based on isotope distribution.