Answer:
B. 204 amu
Explanation:
Given:
Isotopes of Thallium and % abundances
Tl-203 : 29.5%
Tl-205: 70.5%
Formula:
Relative atomic mass = [tex]\sum (Isotope mass * abundance)/100[/tex]
It is given by the summation of the product of all the isotope masses and their % abundances
For Thallium:
Relative atomic mass = [tex][203*29.5 + 205*70.5]/100 = 204.41 amu[/tex]
Since the number of significant digits is 3, the relative atomic mass = 204 amu
