13 I S O T O P E S

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<ul><li> 1. ISOTOPIC NOTATION isotopes are atoms with the same number of protons but different number of neutrons <ul><li>A </li></ul></li></ul> <ul><li>ZX </li></ul> <ul><li>A= mass number </li></ul> <ul><li>(the total number of protons + neutrons) </li></ul> <ul><li>Z= atomic number </li></ul> <ul><li>(the total number of protons) </li></ul> <ul><li>X= element symbol </li></ul> <p> 2. 3. READING ISOTOPIC NOTATION </p> <ul><li>46 </li></ul> <ul><li>21Sc </li></ul> <ul><li>46= mass number </li></ul> <ul><li>(the total number of protons ( 21 ) + neutrons ( 25 ) </li></ul> <ul><li>21= atomic number </li></ul> <ul><li>(the total number of protons ( 21 )) </li></ul> <ul><li>Sc= element symbol </li></ul> <ul><li>In a neutral atom, the number of electrons ( 21 ) is equal to the number of protons. </li></ul> <p> 4. PRACTICE PROBLEMS </p> <ul><li>15 N </li></ul> <ul><li>#protons= ____#neutrons = ____# electrons= ___ </li></ul> <ul><li>35 P </li></ul> <ul><li># p = ____# n= ____#e- = ___ </li></ul> <ul><li>62 Cu 2+ </li></ul> <ul><li># p = ____# n= ____#e- = ___ </li></ul> <ul><li>76 Se 3- </li></ul> <ul><li># p = ____# n= ____#e- = ___ </li></ul> <p>7 8 7 15 20 15 29 33 27 34 42 37 5. Writing ISOTOPIC NOTATION </p> <ul><li>Write the symbol for the atom with an atomic number of 21 and a mass number of 48. </li></ul> <ul><li>Give the complete chemical notation for the nuclide with 23 protons, 26 neutrons and 20 electrons. </li></ul> <ul><li>Write the isotopic notation for </li></ul> <ul><li><ul><li><ul><li>Z = 46 A = 110 </li></ul></li></ul></li></ul> <ul><li><ul><li><ul><li>An atom containing 24 protons, 28 neutrons, and 21 electrons </li></ul></li></ul></li></ul> <ul><li><ul><li><ul><li>Titanium-50 </li></ul></li></ul></li></ul> <p>48Sc 49 V 3+ 110 Pd 52 Cr 3+ 50 Ti 6. PRACTICE PROBLEMS </p> <ul><li>196Pt 4+ </li></ul> <ul><li># p = _____ # n = _____#e- = _____ </li></ul> <ul><li>mass number = ________atomic number = _______ </li></ul> <ul><li>atomic mass = ________name of element = _______ </li></ul> <ul><li>2. Indicate the appropriate atomic mass of an element with 30 protons, 30 neutrons, and 28 electrons. </li></ul> <p>78 118 74 196 78 195.1 amu platinum 65.39 amu 7. Atomic Mass </p> <ul><li>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 1.0079 amu (atomic mass units).The atomic mass is calculated by adding the % of1 H mass found in nature to the % of2 H mass found in nature plus the % of3 H mass. </li></ul> <ul><li>%1 H + %2 H + %3 H = average mass (atomic mass) </li></ul> <ul><li>Generally the formula used is: </li></ul> <ul><li>% X + % Y + % Z = atomic mass. </li></ul> <ul><li>An instrument called the mass spectrometer is generally used to determine the percentages and individual masses of each isotope. </li></ul> <p> 8. Atomic Mass </p> <ul><li>Silver is found to have two stable isotopes, one has an atomic mass of 106.904 amu and the other weighs 108.905 amu.The first isotope represents 51.82 % of the mass of the element and the second represents 48.18 %.What is the atomic mass of the element silver? </li></ul> <ul><li>The equation to use is%X + % Y = average </li></ul> <ul><li>And remember to turn your percents into fractions before multiplying. </li></ul> <ul><li>(0.5182) 106.904 amu + (0.4818) 108.905 amu =? </li></ul> <ul><li>55.398 amu + 52.470 amu =? </li></ul> <ul><li>107.868 amu!!</li></ul> <ul><li>Now look at the periodic table to verify the answer. </li></ul> <p> 9. PRACTICE PROBLEMS # 8 </p> <ul><li>1 .A sample of neon contains three isotopes, neon-20 (with an isotopic mass of 19.9924 amu), neon-21 (20.9939 amu) and neon-22 (21.9914 amu).The natural abundances of these isotopes are 90.92%, 0.257 %, and 8.82 %.Calculate the atomic weight of neon. </li></ul> <ul><li>2.There are only two naturally occuring isotopes of copper,63 Cu and65 Cu.Copper has an atomic mass of 63.55 amu.What is the natural abundance of each isotope? </li></ul> <ul><li>3.There are only two naturally occuring isotopes of gallium, 69Ga and 71Ga.What is the natural abundance of each isotope? </li></ul> <p>20.17 amu 65 Cu = 30%&amp;63 Cu = 70% 69 Ga = 60% and71 Ga = 40% 10. 11. GROUP STUDY PROBLEM #8 </p> <ul><li>_______1.The element with atomic number 53 contains </li></ul> <ul><li>a)53 neutronsb)53 protonsC)26 neutrons &amp; 27 protons d)26 protons &amp; 27 neutrons </li></ul> <ul><li>_______2.The mass of one atom of an isotope is 9.746 x 10 -23g.One atomic mass unit has the mass of 1.6606 x 10 -24g.The atomic mass of this isotope is </li></ul> <ul><li>a)5.870 amu b)16.18 amu c)58.69 amu d)1.627 amu </li></ul> <ul><li>108 </li></ul> <ul><li>_______3.The number of neutrons in an atom of47 Agis </li></ul> <ul><li>a)47 b)108 c)155 d)61 </li></ul> <ul><li>27 </li></ul> <ul><li>_______4.The number of electrons in an ion of 13Al 3+ is </li></ul> <ul><li>a)13 b)10 c)27 d)14 </li></ul> <ul><li>_______5.What is the relative atomic mass of boron if two stable isotopes of boron have the following mass and abundance: </li></ul> <ul><li>10.0129 amu (19.91%)&amp;11.0129 (80.09%) </li></ul> <ul><li>a)10.81 amu b)10.21 amuc)10.62 amud)10.51 amu </li></ul> <p> 12. </p>