1 / 6

More about isotopes

More about isotopes. Atomic mass vs average atomic mass or atomic weight. Atomic Mass. The mass of a specific isotope of an element expressed in atomic mass units (amu) The atomic mass is the total mass of the protons, neutrons and electrons in the atom Atomic mass = mass of an atom

Download Presentation

More about isotopes

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. More about isotopes Atomic mass vs average atomic mass or atomic weight

  2. Atomic Mass • The mass of a specific isotope of an element expressed in atomic mass units (amu) • The atomic mass is the total mass of the protons, neutrons and electrons in the atom • Atomic mass = mass of an atom • This is what we refer to in our isotope expression, eg.

  3. Average Atomic Mass (also called Atomic Weight) Atomic Number Symbol of element Atomic Weight 1 H 1.008 This is the number that you see in the periodic table. This is the weighted average of the all of the isotopes of Hydrogen

  4. What is a Weighted Average? • The isotopes of an element do not occur with equal frequency or amounts • For example, the relative abundances for the three carbon isotopes are: • carbon-12 98.9% • carbon-13 1.1%, • carbon-14 <001%. • The "average" mass for the atoms of an element is dictated by the most abundant or common isotope • The atomic weights in the periodic table = weighted averages • Tabulated atomic weight value doesn't match any actual atom, but is closer to the weight for the most common isotope • We’ll follow the steps of how to calculate a weighted average next….

  5. Calculating Weighted Average weighted average = ( decimal fraction A) mass A + ( decimal fraction B) mass B • Carbon-12 atomic mass = 12 amu; abundance = 98.9% • Carbon-13 atomic mass = 13 amu; abundance = 1.1% • Carbon-14 atomic mass = 14 amu; abundance = 0.001% Atomic weight = (0.989 * 12) + (0.011 * 13) + (0.00001 * 14) = 12.011 6 C 12.011

  6. Average Atomic Mass Worksheet Homework - I will post answers on website Monday. You will have to show ALL of your work.

More Related