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Atomic Mass Formula:
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Atomic mass (also called atomic weight) is the average mass of atoms of an element, calculated using the relative abundance of isotopes in a naturally-occurring element. It is expressed in atomic mass units (amu), where 1 amu is defined as 1/12th the mass of a carbon-12 atom.
The calculator uses the atomic mass formula:
Where:
Explanation: The equation accounts for the weighted average of all naturally occurring isotopes of an element based on their relative abundances.
Details: Atomic mass is fundamental in chemistry for stoichiometric calculations, determining molar masses of compounds, and understanding isotopic composition. It's essential for chemical reactions, analytical chemistry, and nuclear physics applications.
Tips: Enter the abundance (as percentage) and mass (in amu) for each isotope. You can add multiple isotopes to calculate the weighted average atomic mass. Ensure the total abundance is 100% for accurate results.
Q1: Why is atomic mass not a whole number?
A: Atomic mass is a weighted average of all naturally occurring isotopes of an element, accounting for their different masses and abundances.
Q2: What's the difference between mass number and atomic mass?
A: Mass number is the sum of protons and neutrons in a specific isotope (always a whole number), while atomic mass is the weighted average of all isotopes.
Q3: Why is carbon-12 used as the standard?
A: Carbon-12 was chosen as the reference because it's a stable, abundant isotope that forms strong covalent bonds, making it ideal for mass spectrometry.
Q4: How precise are atomic mass values?
A: Modern atomic mass values are extremely precise, often to 8-10 decimal places, as determined by mass spectrometry.
Q5: Do atomic masses change over time?
A: The standard atomic weights of some elements vary in different samples due to natural variations in isotopic composition.