Chapter 3. Elements Periodic Table Compounds. Elements. All words in the English language are the result of the 26 letters of the alphabet. All substances on our planet and the universe are the result of about 88 known “building blocks” called the elements. Why 88?. Elements.
Example: Chlorine has only two known isotopes – Cl-35 and Cl-37. Cl-35 is found 75.5% of the time and Cl-37 is found 24.5% of the time.
Isotope Mass X Percent = Contribution
(approximate) to total mass
35 amu X 0.755 = 26.4 amu
37 amu X 0.245 = 9.1 amu
Totals 1.000 35.5 amu