mass number
1
4.9
- noun
- /mæs ˈnʌmbər/
- Specialized
:
número de masa
- Thus, the vertical axis really gives mass number A, and the horizontal axis gives A minus atomic number Z, which is the number of neutrons.
Examples
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The mass number of an atom is calculated by adding the number of protons and neutrons in its nucleus.
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In a periodic table, the mass number indicates the total count of protons and neutrons in an atom.
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The listed numbers are the mass number, and each isotope has a different mass number.
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The listed numbers are the mass number, and each isotope has a different mass number.
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A is that mass number of whatever the neutrons are hitting and that one comes directly from the neutron mass number.
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For carbon-12, the mass number is 12, comprising six protons and six neutrons.
Synonyms
The total number of protons and neutrons in an atom's nucleus
Surface Forms
Morphology
Combining 'mass' (amount of matter) and 'number' (a count) gives an intuitive sense that this is a numerical property related to mass, so a learner who knows the words will grasp it refers to some number associated with mass. However, the precise scientific meaning — the count of protons and neutrons in the nucleus — is a specialized definition not directly derivable from the constituents alone, so it requires domain knowledge beyond basic word meanings.
Etymology
Mass number comes from the simple idea of counting the parts that give an atom its mass: the protons and neutrons in its tiny center. So the word number means 'how many', and the whole phrase means the total count of those particles, which shows how 'heavy' the atom is.