+ ISOTOPIC NOTATION isotopes are atoms with the same number of protons but different number of neutrons

+ Other ways to write elements: ClCl-36 Atomic Number Mass Number

ISOTOPES isotopes are atoms with the same number of protons but different number of neutrons

ISOTOPES isotopes are atoms with the same number of protons but different number of neutrons

+ Isotope Properties 1)Isotopes of an element have same number and distribution of electrons, hence they undergo the same chemical (and physical) reactions. 2)Differences in mass can, however, influence the rate or extent of chemical or physical reactions, or lead to partitioning of isotopes differentially among phases.

+ READING ISOTOPIC NOTATION Sc 46 = mass number (the total number of protons (21) + neutrons (25) 21 = atomic number 21 (the total number of protons (21)) Sc = element symbol In a neutral atom, the number of electrons (21) is equal to the number of protons.

Example: Isotopes of Carbon and Hydrogen protium deuteriumtritium H H H Isotopes of Carbon Isotopes of Hydrogen

+ Writing ISOTOPIC NOTATION 1. Write the symbol for the atom with an atomic number of 21 and a mass number of Give the complete chemical notation for the nuclide with 23 protons, 26 neutrons and 23 electrons. 3. Write the isotopic notation for a. Z = 46A = 110 b. An atom containing 24 protons, 28 neutrons, and 21 electrons 48 Sc 49 V 110 Pd 52 Cr

+ PRACTICE PROBLEMS Pt 4+ # p = _____# n = _____ #e- = _____ mass number = ________ atomic number = _______ atomic mass = ________ name of element = _______ 2. Indicate the appropriate atomic mass of an element with 30 protons, 30 neutrons, and 28 electrons amu platinum amu

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Atomic Mass The atomic mass of an element represents the average mass of all the isotopes found in nature. No element exists with only one possible isotope. Hydrogen has the smallest number of isotopes: 1 H protium, 2 H deuterium, 3 H tritium. Its atomic mass is amu (atomic mass units). The atomic mass is calculated by adding the % of 1 H mass found in nature to the % of 2 H mass found in nature plus the % of 3 H mass. % 1 H + % 2 H + % 3 H = average mass (atomic mass) Generally the formula used is: % X + % Y + % Z… = atomic mass. An instrument called the mass spectrometer is generally used to determine the percentages and individual masses of each isotope.

Atomic Mass Silver is found to have two stable isotopes, one has an atomic mass of amu and the other weighs amu. The first isotope represents % of the mass of the element and the second represents %. What is the atomic mass of the element silver? The equation to use is %X + % Y = average And remember to turn your percents into fractions before multiplying. (0.5182) amu + (0.4818) amu =? amu amu =? amu !! Now look at the periodic table to verify the answer.

PRACTICE PROBLEMS # 8 1. A sample of neon contains three isotopes, neon-20 (with an isotopic mass of amu), neon-21 ( amu) and neon-22 ( amu). The natural abundances of these isotopes are 90.92%, %, and 8.82 %. Calculate the atomic weight of neon. 2. There are only two naturally occuring isotopes of copper, 63 Cu and 65 Cu. Copper has an atomic mass of amu. What is the natural abundance of each isotope? 3. There are only two naturally occuring isotopes of gallium, 69Ga and 71Ga. What is the natural abundance of each isotope? amu 65 Cu = 30% & 63 Cu = 70% 69 Ga = 60% and 71 Ga = 40%

GROUP STUDY PROBLEM #8 What is the relative atomic mass of boron if two stable isotopes of boron have the following mass and abundance: amu (19.91%) & (80.09%) a) amub) amu c) amu d) amu