The average atomic mass of fictitious element Z is 261.4 amu. Z has only 2 isotopes. One of its isotopes has an atomic mass of 260.0 amu the other 264.0 amu. Choose the abundance for the isotopes 55%

44%

35%

99%

25%

1%

11%

65%

The abundance for the isotopes = 65%(isotope 1) and 35%(isotope 2)

The elements in nature have several types of isotopes

Isotopes are atoms whose no-atom has the same number of protons while still having a different number of neutrons.

So Isotopes are elements that have the same Atomic Number (Proton)

Atomic mass is the average atomic mass of all its isotopes

Mass atom X = mass isotope 1 . % + mass isotope 2.%

The average atomic mass of fictitious element Z is 261.4 amu

isotopes 1 = 260, x%

isotopes 2 = 264, 100-x%

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