mass defect

noun

: the difference between the mass of an isotope and its mass number expressed in atomic mass units and being either positive or negative

the mass defect of the carbon isotope₆C¹², mass 12.00388, is +0.00388, while that of phosphorus₁₅P³¹, isotopic mass 30.984, is −0.016

compare binding energy, packing fraction

The Ultimate Dictionary Awaits

Expand your vocabulary and dive deeper into language with Merriam-Webster Unabridged.

1. Expanded definitions
2. Detailed etymologies
3. Advanced search tools
4. All ad-free

Discover what makes Merriam-Webster Unabridged the essential choice for true word lovers.

Start Your Free Trial Now