Final answer:
Boron-11 has 5 protons and 6 neutrons. The atomic mass of boron is calculated by considering the relative abundances of its isotopes, resulting in an atomic mass of 10.8 amu.
Step-by-step explanation:
An atom of boron-11 consists of 5 protons and 6 neutrons. The atomic number, which indicates the number of protons in an atom's nucleus, is 5 for all boron atoms. As for neutrons, boron-11 has 6 neutrons, which is derived from the isotope's mass number (11) minus the number of protons (5).
The atomic mass of boron takes into account the relative abundances of its isotopes. The calculation involves multiplying the mass of each isotope by its relative abundance and then adding these values together. For boron, this would be calculated as ((0.20) x (10)) + ((0.80) x (11)), resulting in an atomic mass of 10.8 amu.
Boron Isotopes
Boron has two naturally occurring isotopes: boron-10 and boron-11. In any sample of boron, approximately 20% would be boron-10, which has 5 neutrons, and 80% would be boron-11, with 6 neutrons. Boron's atomic mass averages out to about 10.8 amu because of the proportions of these isotopes.