+**Be9** refers to [Beryllium](/wiki/Beryllium)-9, the sole stable [isotope](/wiki/Isotope) of the element beryllium. Composed of four protons and five neutrons, it forms a light and resilient atomic nucleus.
+## See also
+- [Element](/wiki/Element)
+- [Nucleus](/wiki/Nucleus)
+- [Atomic Mass](/wiki/Atomic_Mass)
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