Answer: 207.24
Explanation: Atomic mass = no of protons + no of neutrons
1) 82 protons, 122 neutrons , mass number= 82+122 = 204
2) 82 protons, 125 neutrons, mass number= 82+125 = 207
3) 82 protons, 124 neutrons, mass number= 82+124 = 206
4) 82 protons, 126 neutrons, mass number= 82+126 = 208
Average atomic mass of an element = [tex]\sum(\text{atomic mass of an isotopes}\times {{\text {fractional abundance}}[/tex]
Average atomic mass of given element = [tex](204\times 0.014+207\times 0.221 +206\times 0.241+208\times 0.524)=207.24[/tex]
The approximate atomic mass of lead is 207.24.
Answer:
207.2 g/mol
Explanation:
To answer this question you must know the atomic mass of one proton and one neutron are both 1 g/mol. Thus, mass of each isotope is:
²⁰⁴Pb: 82×1g/mol + 122×1g/mol = 204 g/mol
²⁰⁷Pb: 82×1g/mol + 125×1g/mol = 207 g/mol
²⁰⁶Pb: 82×1g/mol + 124×1g/mol = 206 g/mol
²⁰⁸Pb: 82×1g/mol + 126×1g/mol = 208 g/mol
Atomic mass is the pondered average of mass of isotopes. Thus, atomic mass of lead is:
204 g/mol × 0.014 + 207 g/mol × 0.221 + 206 g/mol × 0.241 + 208 g/mol × 0.524 =
207.2 g/mol
