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Hello!
To find the average atomic mass of the given isotopes of lead, we need to use the formula: Average Mass = (mass of iso-1)(% of iso-1) + (mass of iso-2)(% of iso-2) + (mass of iso-3)(% of iso-3) + ...
The ellipsis means that you can keep on multiplying the mass of an isotope and the percentage of an isotope together and add them until all of the isotopes of a given element is used.
First off, we cannot multiply by a percentage, so we need to convert it into a decimal. All percentages are out of 100, so we divide the percentage by 100 to get it to a decimal.
1) 1.37 / 100 = 0.0137
2) 26.6 / 100 = 0.266
3) 20.82 / 100 = 0.2082
4) 51.55 / 100 = 0.5155
With all of the percentages converted to decimals, we can use our formula to solve for the average atomic mass.
Remember to round to the number of significant figures! In all of the given numbers, when multiplying, the largest number of significant figures is 3. But, when you add numbers, the significant figure is stops at is at the least number of decimal places (for example: 1 + 0.1 = 1 -- because the least number of decimal places is no decimal places).
Average Mass = (204 amu)(0.0137) + (206)(0.266) + (207)(0.2082) + (208)(0.5155)
= 2.79 + 54.8 + 43.1 + 107
= 207.69 → 207 (the least number of decimal places is no decimal places)
Therefore, lead's approximate atomic mass is 207 amu.
Considering the definition of atomic mass, isotopes and atomic mass of an element, the average mass of Pb is 207.9122.
First of all, atomic mass (A) is the mass of an atom, which is made up of the total mass of protons and neutrons.
The same chemical element can be made up of different atoms, that is, its atomic number is the same, but the number of neutrons is different. These atoms are called isotopes of the element.
Therefore, isotopes are atoms with different numbers of neutrons but the same number of protons. Therefore, the mass of each isotope is different.
On the other hand, the relative atomic mass of an element corresponds to the average of the masses of the isotopes of each element. That is, the atomic masses of chemical elements are usually calculated as the weighted average of the masses of the different isotopes of each element, taking into account the relative abundance of each of them.
In this case, Pb-204 is 1.37% abundant, Pb-206 is 26.6% abundant, Pb-207 is 20.82% abundant and Pb-208 is 51.55% abundant. Then, the average mass of Pb can be calculated as:
204×0.0137 + 206×0.266 + 207×0.2082 + 208×0.5155= 207.9122
Finally, the average mass of Pb is 207.9122.
Learn more:
- brainly.com/question/14403750?referrer=searchResults
- brainly.com/question/10043246?referrer=searchResults
- brainly.com/question/15553207?referrer=searchResults
