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ISOTOPIC NOTATION isotopes are atoms with the same number of protons but different number of neutrons A Z X A = mass number (the total number of protons + neutrons) Z = atomic number (the total number of protons) X = element symbol

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READING ISOTOPIC NOTATION Sc 46 = mass number 2125 (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.

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PRACTICE PROBLEMS 15 N # protons = ____ # neutrons = ____ # electrons = ___ 35 P # p = ____ # n= ____ #e- = ___ 62 Cu 2+ # p = ____ # n= ____ #e- = ___ 76 Se 3- # p = ____ # n= ____ #e- = ___

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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 20 electrons. 3. Write the isotopic notation for a. Z = 46A = 110 b. An atom containing 24 protons, 28 neutrons, and 21 electrons c. Titanium Sc 49 V Pd 52 Cr Ti

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PRACTICE PROBLEMS Pt 4+ # p = _____# n = _____ #e- = _____ mass number = ________ atomic number = _______ atomic mass = ________ name of element = _______ 2. Indicate the appropriate average 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: % A + % B + % C… = atomic mass. An instrument called the mass spectrometer is generally used to determine the percentages and individual masses of each isotope.

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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.

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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. Which is the most abundance isotope? 3. There are only two naturally occuring isotopes of gallium, 69Ga and 71Ga. Which is the most abundance isotope? amu 65 Cu = 30% & 63 Cu = 70% 69 Ga = 60% and 71 Ga = 40%

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GROUP STUDY PROBLEM #8 _______1. The element with atomic number 53 contains a) 53 neutrons b) 53 protons C) 26 neutrons & 27 protons d) 26 protons & 27 neutrons 108 _______2. The number of neutrons in an atom of 47 Ag is a) 47b) 108c) 155d) _______3. The number of electrons in an ion of 13 Al 3+ is a) 13b) 10c) 27d) 14 Calculators _______4. 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

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