Final answer:
The atomic mass of boron with isotopes B-10 (19.78%) and B-11 (82.22%) is approximately 11.02 amu. The mass number of B-10 is 10, and for B-11, it is 11.
Step-by-step explanation:
To calculate the atomic mass of boron, which has two naturally occurring isotopes, we use the relative percentages of each isotope and their respective atomic masses. The isotopes are B-10 with a mass of 10 amu (atomic mass units) and B-11 with a mass of 11 amu. The percentage of B-10 is 19.78% and B-11 is 82.22%.
The formula to calculate the average atomic mass is:
Atomic mass = (% abundance of isotope 1 × atomic mass of isotope 1) + (% abundance of isotope 2 × atomic mass of isotope 2)
First, we convert the percentages to decimal form:
Then, applying these values to the formula:
Atomic mass = (0.1978 × 10) + (0.8222 × 11) = 1.978 + 9.0442 = 11.0222 amu
The number is typically rounded to a certain number of decimal places based on the precision of the given percentages. So, the boron average mass is approximately 11.02 amu.
The mass number, also known as the nucleon number, indicates the total number of protons and neutrons in the nucleus for a given isotope. Therefore, the mass numbers for the isotopes B-10 and B-11 are 10 and 11, respectively.