Doing Calculations The metal thallium occurs naturally as 30 percent thallium-203 and 70 percent thallium-205. Calculate the atomic mass of thallium. Enter your numerical answer in
the blank provided please help

Average atomic mass of thallium = 204.4 amu.

Explanation:

Given data:

Abundance of thallium-203 = 30%

Abundance of thallium-205 = 70%

Average atomic mass = ?

Solution:

Average atomic mass of thallium = (abundance of 1st isotope × its atomic mass) +(abundance of 2nd isotope × its atomic mass)  / 100

Average atomic mass of thallium = (30%×203)+(70%×205) /100

Average atomic mass of thallium =  6090 + 14350 / 100

Average atomic mass of thallium = 20440 / 100

Average atomic mass of thallium = 204.4 amu.

why do the isotopes of a particular element behave differently in nuclear reactions but the same in chemical reactions? chemical reactions involve changes to electrons in an atom; isotopes do not differ in electrons, and so they react the same way during chemical changes.