in nature, 51% of bromine atoms are bromine-79 and the other 49% are bromine-81. what is the mass number for each of these isotopes
Huh? The mass numbers are 79, and 81.
the avg atomic mass will be .51*79+.49*81
Are you proofing your typing? Your question makes no sense.
To determine the mass number for each isotope, we need to understand what a mass number is. The mass number of an isotope represents the total number of protons and neutrons in the nucleus of an atom.
1. Start by recognizing that bromine-79 and bromine-81 are isotopes of bromine. This means they have the same number of protons (35) but a different number of neutrons.
2. We know that 51% of bromine atoms are bromine-79, so let's calculate the mass number for bromine-79. Recall that the mass number is the sum of protons and neutrons.
- Percentage of bromine-79 = 51%
- Percentage of bromine-81 = 49%
3. The average atomic mass of bromine (which is found on the periodic table) takes into account the abundance of each isotope. It can be calculated using the following formula:
Average atomic mass = (mass isotope A × abundance isotope A) + (mass isotope B × abundance isotope B) + ...
Let's apply this formula to find the average atomic mass of bromine:
- For bromine-79: Mass number is 79, and abundance is 51% (or 0.51).
- For bromine-81: Mass number is 81, and abundance is 49% (or 0.49).
Thus, the average atomic mass of bromine can be calculated as follows:
Average atomic mass = (79 × 0.51) + (81 × 0.49)
= 40.29 + 39.69
= 80.98
Therefore, the average atomic mass of bromine is approximately 80.98.
4. Now we have the average atomic mass of bromine and the mass numbers for bromine-79 and bromine-81. We can calculate the difference between the average atomic mass and the mass number of each isotope to find the number of neutrons.
For bromine-79:
Neutrons = Mass number - Atomic number
= 79 - 35
= 44 neutrons
For bromine-81:
Neutrons = Mass number - Atomic number
= 81 - 35
= 46 neutrons
Therefore, the mass numbers for bromine-79 and bromine-81 are 79 and 81, respectively, and they have 44 and 46 neutrons, respectively.