Question

Element z has two natural isotopes: z-79 (78.918 amu) and z-81 (80.916 amu). calculate the atomic mass of element z given the abundance of z-81 is 49.31%.

Answer 1

The average atomic mass of element Z with two isotopes Z-79 and Z-81 is calculated using their atomic masses and abundances, resulting in approximately 79.91 amu.

Step-by-step explanation:

The calculation of the atomic mass of element Z, which has two natural isotopes Z-79 and Z-81, involves using their respective atomic masses and the given abundances. The abundance of Z-81 is 49.31%, which means the abundance of Z-79 is 100% - 49.31% = 50.69%. To find the average atomic mass we use the formula:

Average Atomic Mass = (mass of isotope 1 × abundance of isotope 1) + (mass of isotope 2 × abundance of isotope 2)

For Z-79 and Z-81, the equation would be:

Average Atomic Mass = (78.918 amu × 0.5069) + (80.916 amu × 0.4931)

Doing the math gives us:

Average Atomic Mass = (39.99987 amu) + (39.91045 amu) = 79.91032 amu

Thus, the average atomic mass of element Z is approximately 79.91 amu.

Answer 2

isotopes are atoms of the same element with different number of neutrons, hence different mass numbers.
relative atomic mass is the weighted average atomic masses of the isotopes.
atomic mass of element z =78.918 amu x (100-49.31)%+ 80.916 amu x 49.31%
atomic mass = (78.918 x 50.69%) + (80.916 x 49.31%)
= 40.00 + 39.90
atomic mass of element z = 79.90