14 Isotope Notation Can also be written as ELEMENT – MASS # Example: Carbon - 12
15 So, why do the elements on the PT have masses with decimals???
16 AVERAGE ATOMIC MASSThe weighted average mass of all naturally occurring isotopes of an element.
17 Example using exam scores! Exam Scores can be weighted higher than homework or quiz grades:What if… And you received:Exam 50% Exam 93Quizzes 20% Quizzes 82.5Homework 30% Homework 85Your grade =(93 x .5) + (82.5 x .2) + (85 x .3) = 88.5
18 ExampleExample: The element hydrogen has three isotopes. It exists in nature 99.41% of the time as Hydrogen-1, 0.4% of the time as Hydrogen-2 and 0.19% of the time as Hydrogen – 3. What is the average atomic mass of hydrogen?0.9995* * *3 = u
20 Democritus (400 B.C.)First to develop the idea of an atom.
21 DALTON Dalton created an atomic theory that stated: All elements are composed of tiny indivisible particles called atomsAtoms of the same element are identical. The atoms of any one element are different from those of any other element