1. ISOTOPES Chemistry

2. Isotope Definition: A different form of an element. Proton number is the same as the other forms or isotopes. Electron number is the same as the other forms or isotopes. Neutron number is DIFFERENT than the other forms or isotopes. Different atomic mass (because different # of neutrons!) Different isotopes have different characteristics and uses_. Some isotopes are found in nature, some are man-made for certain purposes.

3. Symbols for Isotopes Isotopes Symbol components 1. Element symbol 2. Mass number (Different for Different isotopes; = #P + #N) 3. #P (same for each isotope) C 14 6

4. Naming isotopes How you name an isotope: Element name – Mass # Examples: Carbon-14, Carbon-12, Carbon-13

5. Isotope Symbols: Your turn to practice Write the isotope symbol for each of the following isotopes using the given information and the information on the previous slides: Isotope Symbol (without help boxes) Information 1. Lithium-4 Or: Mass # = #P + #N = 4 Element symbol: Li #P = 3 (atomic #) 2. Lithium-6Or: Mass # = #P + #N = 6 Element symbol: Li #P = 3 (atomic #) 3. Lithium-7Or: Mass # = #P + #N = 7 Element symbol: Li #P = 3 (atomic #) Li 4343 6363 7373 7373 6363 4343

6. Examples of Isotopes and Uses Carbon-12(6P, 6N, 6E) Stable in nature Most abundant isotope of carbon (about 99% of carbon found in nature) In all carbon-based life (humans, animals, plants), common element in food – carbohydrates, etc., in ALL living things! Carbon-13 (6P, 7N, 6E) Stable in nature Common, but less abundant in nature than C-12 (about 1% of carbon found in nature) Carbon-14 (6P, 8N, 6E) Unstable in nature Used to data artifacts because it’s radioactive and decays over a certain amount of time – you can tell how old something is

7. Isotope Calculations Atomic mass of isotope: Grams of 1 mole of that isotope (Average mass of 1 atom of that isotope) How you find it: Atomic mass =Mass of a sample of atoms # of atoms in that sample Percent Abundance of an certain isotope: By Mass: Mass of a sample of the isotope x 100% Total mass of the entire sample OR By Number: Number of atoms in that sample x 100% Total number of atoms of entire sample

8. Isotope Calculations Weighted average atomic mass of the element Average atomic mass of the element taking into account the relative percent abundances of different isotopes of that element This is how they calculate the atomic mass of an element on the periodic table of elements! How you calculate it: Weighted average atomic mass = (atomic mass for isotope 1) x (decimal abundance for isotope 1) + (atomic mass for isotope 2) x (decimal abundance for isotope 2) +… (atomic mass for isotope “n”) x (decimal abundance for isotope “n”) *Remember the decimal percent abundance is just the percent abundance before multiplying it by 100%