Answer: 86.14%, 100.86%
Step-by-step explanation:
The relative atomic mass of an element is the average mass of the isotopes of the element, taking into account the abundance of each isotope. To determine the percentage abundance of each isotope, we can use the following formula:
Percentage abundance = (isotope mass / relative atomic mass) x 100
For the isotope with mass number 6, the percentage abundance would be:
(6 / 6.94) x 100 = 86.14%
For the isotope with mass number 7, the percentage abundance would be:
(7 / 6.94) x 100 = 100.86%
So the isotope with mass number 6 has an 86.14% abundance, and the isotope with mass number 7 has a 100.86% abundance. The sum of these two percentages is slightly greater than 100 because the relative atomic mass is an average and does not take into account the abundance of each isotope.