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The Structure of the Atom

The Structure of the Atom. Atoms are composed of protons, neutrons, and electrons Proton - positive (p) Neutron - neutral (n) Electron - negative (e-) Nucleus - protons & neutrons Electrons - around the nucleus in an electron cloud. Sub Atomic Particals.

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The Structure of the Atom

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  1. The Structure of the Atom • Atoms are composed of protons, neutrons, and electrons • Proton - positive (p) Neutron - neutral (n) Electron - negative (e-) • Nucleus - protons & neutrons Electrons - around the nucleus in an electron cloud

  2. Sub Atomic Particals • Protons Electrons Neutrons • Protons and Neutrons are assigned as having 1amu for each partical. • Electrons are negligible and therefore not counted in the mass of an element. • 1 amu = 1 g/mol

  3. If atomic mass is proton + neutrons why is the mass not an even # and has value after the decimal.

  4. Isotopes and Nuclides

  5. ISOTOPIC NOTATIONisotopes 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

  6. READING ISOTOPIC NOTATION 46 21 Sc 46 = mass number (the total number of protons (21) + neutrons (25) 21 = atomic number (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.

  7. Ions • An ion is an atom that has gained or lost one or more electrons and acquired a net electrical charge • Charge of ion = # of protons minus # of electrons (Make sure you keep the sign) • Place the charge in the upper right corner of the chemical symbol. Ex. Mg2+ • Positive ions - cation • Negative ions - anion

  8. PRACTICE PROBLEMS 7 8 7 15N # protons = ____ # neutrons= ____ #electrons = ___ 35P # p = ____ # n= ____ #e- = ___ 62Cu2+ # p = ____ # n= ____ #e- = ___ 76Se3- # p = ____ # n= ____ #e- = ___ 15 20 15 27 29 33 42 34 37

  9. Writing ISOTOPIC NOTATION 48 Sc • Write the symbol for the atom with an atomic number of 21 and a mass number of 48. • Give the complete chemical notation for the nuclide with 23 protons, 26 neutrons and 20 electrons. • Write the isotopic notation for • Z = 46 A = 110 • An atom containing 24 protons, 28 neutrons, and 21 electrons • Titanium-50 49V3+ 110Pd 52Cr3+ 50Ti

  10. PRACTICE PROBLEMS 74 118 78 • 196 Pt4+ # 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. 78 196 195.1 amu platinum 65.39 amu

  11. 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: 1H protium, 2H deuterium, 3H tritium. Its atomic mass is 1.0079 amu (atomic mass units). The atomic mass is calculated by adding the % of 1H mass found in nature to the % of 2H mass found in nature plus the % of 3H mass. • % 1H + % 2H + % 3H = 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.

  12. Atomic Mass • Silver is found to have two stable isotopes, one has an atomic mass of 107 amu and the other weighs 109 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? The equation to use is %X + % Y = average And remember to turn your percents into fractions before multiplying. (0.5182) 106.904 amu + (0.4818) 108.905 amu =? 55.398 amu + 52.470 amu =? 107.868 amu !! Now look at the periodic table to verify the answer.

  13. PRACTICE PROBLEMS # 8 1. A sample of neon contains three isotopes, neon-20, neon-21 and neon-22. The natural abundances of these isotopes are 90.92%, 0.257 %, and 8.82 %. Calculate the atomic weight of neon. 2. There are only two naturally occuring isotopes of copper, 63Cu and 65Cu. Copper has an atomic mass of 63.55 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? 20.17 amu 65Cu = 30% & 63Cu = 70% 69Ga = 60% and 71Ga = 40%

  14. 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 _______2. The mass of one atom of an isotope is 9.746 x 10-23 g. One atomic mass unit has the mass of 1.6606 x 10-24 g. The atomic mass of this isotope is a) 5.870 amu b) 16.18 amu c) 58.69 amu d) 1.627 amu 108 _______3. The number of neutrons in an atom of 47 Ag is a) 47 b) 108 c) 155 d) 61 27 _______4. The number of electrons in an ion of 13 Al3+ is a) 13 b) 10 c) 27 d) 14 _______5. What is the relative atomic mass of boron if two stable isotopes of boron have the following mass and abundance: 10.0129 amu (19.91%) & 11.0129 (80.09%) a) 10.81 amu b) 10.21 amu c) 10.62 amu d) 10.51 amu

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