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Atomic Structure

Explore the fundamental concepts of atomic structure, including the definition of atoms, the history of the atom, subatomic particles, the nucleus, and distinguishing among atoms. Learn about isotopes and how to determine the number of protons, neutrons, and electrons in an atom.

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Atomic Structure

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  1. Atomic Structure www.assignmentpoint.com

  2. Defining the Atom • All elements are composed of particles called atoms • All atoms of the same element are identical • Atoms of different elements combine to form compounds • Atoms of one element can never be changed into another element www.assignmentpoint.com

  3. History of the Atom • Democritus (Greek 460-370 BC) • 1st to use the word atom • Believed that atoms were indivisible & indestructible • No scientific support • Aristotle (Greek 384-322 BC) • Rejected the theory of atoms • Believed in 4 core elements fire, air, water, earth www.assignmentpoint.com

  4. Antoine Lavoisier (French 1743-1794) • Law of Conservation of Matter – Matter is not created or destroyed during a chemical reaction www.assignmentpoint.com

  5. Joseph Proust (French 1754-1826) • Law of Definite Proportions - A compound is always composed of the same elements, in the same proportion by mass www.assignmentpoint.com

  6. John Dalton (English 1766-1844) • Studied the ratio in which elements combine • Quantitative data – mass • Law of Multiple Proportions - When 2 elements form more than one compound, they do so in a ratio of whole numbers www.assignmentpoint.com

  7. Dalton’s Atomic Theory • All elements are composed of indivisible ‘solid sphere’ atoms. • All atoms of a given element are identical. • Atoms of different elements differ in their masses. • Different atoms combine in simple whole number ratios to form compounds. www.assignmentpoint.com

  8. Structure of the Atom www.assignmentpoint.com

  9. Subatomic Particles • Today… Dalton’s Atomic Theory has one important change • Atoms are divisible… • 3 types of subatomic particles • Protons • Neutrons • Electrons www.assignmentpoint.com

  10. Electrons • J.J. Thomson (English 1897) – • Identified the 1st subatomic particle • Cathode-ray tube www.assignmentpoint.com

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  12. Thomson’s Electron Model • Named electrons • Symbol: e- • Charge: (-1) • Mass: ~ 0 amu • Plum Pudding/ Chocolate Chip Cookie www.assignmentpoint.com

  13. What about the protons & neutrons? • Protons • Symbol: p+ • Charge: (+1) • Mass: 1 amu • Neutons • Symbol: n0 • Charge: (0) neutral • Mass: 1 amu www.assignmentpoint.com

  14. The Nucleus • Ernest Rutherford (English 1911) - • Discovered the ‘structure’ of the atom • Gold foil experiment Rutherford’s Gold Foil Experiment www.assignmentpoint.com

  15. Rutherford’s Nuclear Model • Atom is mostly empty space • Atoms have a dense center – nucleus • Most of the mass is in the nucleus • Nucleus has a positive charge • Protons & neutrons are located in the nucleus • Electrons are outside of the nucleus & occupy most of the atom’s volume www.assignmentpoint.com

  16. Distinguishing Among Atoms www.assignmentpoint.com

  17. What makes atoms different from one another? • # of protons • Atomic number = # of protons • Usually written as a subscript Mg12 or 12Mg What element has 11 protons? How many protons does potassium have? Sodium 19 www.assignmentpoint.com

  18. How do you determine the # of neutrons? • Atomic mass = # protons + # neutrons • Usually written as a superscript 12C or C12 or C -12 • # of neutrons is the difference between the atomic mass & the atomic number # of neutrons = atomic mass - atomic # www.assignmentpoint.com

  19. 4.0026… round to 4 What is the atomic mass of helium? What element has an atomic mass of 27? How many protons does this element contain? How many neutrons does this element contain? Aluminum 13 27 – 13 = 14 www.assignmentpoint.com

  20. What about electrons? • # electrons = # of protons • Why? • Atoms are electrically neutral How many electrons does sulfur contain? Which element contains 10 electrons? 16 Neon www.assignmentpoint.com

  21. Sample Problems • How many protons, neutrons and electrons are in each atom? Beryllium (Be) - Fluorine (F) - Hydrogen (H) - 4, 5, 4 9, 10, 9 1, 0, 1 www.assignmentpoint.com

  22. 16 – 8 = 8 • How many neutrons are in each atom? 8O16 47Ag108 82Pb207 108 – 47 = 61 207 – 82 = 125 www.assignmentpoint.com

  23. Express the composition of each atom in shorthand form. Nitrogen -14 Sodium - 23 Phosphorus -31 p+ = 7, n0 = 7, e- = 7 p+ = 11, n0 = 12, e- = 11 p+ = 15 , n0 = 16, e- = 15 www.assignmentpoint.com

  24. Isotopes • Atoms that contain the same number of protons but have different numbers of neutrons • Different atomic masses • Does not change the atom’s identity • Are naturally occurring • Symbols: 11Na23 or 11Na24 6C12 or 6C13 or 6C14 www.assignmentpoint.com

  25. Determine the number of protons, neutrons and electrons in the following: 1H1 1H2 1H3 p+ = 1, n0 = 0, e- = 1 p+ = 1, n0 = 1, e- = 1 p+ = 1, n0 = 2, e- = 1 www.assignmentpoint.com

  26. Determining the Atomic Mass • Atomic mass # is an average of atom’s naturally occurring isotopes Copper has 2 isotopes Cu-63 and Cu-65 Which isotope is most abundant? There are 3 isotopes of Silicon with mass numbers of 28, 29, and 30. Which is more abundant? 63 Si -28 www.assignmentpoint.com

  27. Calculating the Atomic Mass • Multiply the mass of each isotope by its natural abundance (expressed as a decimal), then add the products • Practice… www.assignmentpoint.com

  28. Ions • An atom with an electrical charge • Occurs 2 ways: • Oxidation – loss of an e- results in a (+) charge • Reduction – gain of an e- results in a (-) charge Mnemonic: ‘Leo says Ger’ Loss of electrons = oxidation Gain of electrons = reduction www.assignmentpoint.com

  29. Examples of Ions Lost 1e- • H+ • Cl- • As3- • Mg2+ • Oxidation State – • Number found on the periodic table • Shows the number of e-gained or lost • Many elements have more than one number Gained 1e- Gained 3e- Lost 2e- www.assignmentpoint.com

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