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Atoms and Elements

Atoms and Elements. The Atom Atomic Number and Mass Number Isotopes. The Atom. An atom is the smallest particle that retains the characteristics of an element. Atomic Theory. Atoms are building blocks of elements Similar atoms in each element Different from atoms of other elements

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Atoms and Elements

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  1. Atoms and Elements The Atom Atomic Number and Mass Number Isotopes LecturePLUS Timberlake

  2. LecturePLUS Timberlake

  3. The Atom An atom is the smallest particle that retains the characteristics of an element

  4. Atomic Theory • Atoms are building blocks of elements • Similar atoms in each element • Different from atoms of other elements • Two or more different atoms bond in simple ratios to form compounds LecturePLUS Timberlake

  5. The Parts of the Atom Atoms are composed of three subatomic particles: • Protons have a positive charge (+) • Electrons carry a negative charge (-) • Neutronsare electrically neutral.

  6. Subatomic Particles Particle Symbol Charge Relative Mass Electron e- 1- 0 Proton p+ + 1 Neutron n 0 1 LecturePLUS Timberlake

  7. Location of Subatomic Particles 10-13 cm electrons protons neutrons 10-8 cm nucleus LecturePLUS Timberlake

  8. The Structure of the Atom The protons and neutrons, each with a mass of about 1 amu are found in the tiny, dense nucleus. The electrons are located outside the nucleus.

  9. Models of the Atom

  10. Atomic Number Counts the number of protons in an atom LecturePLUS Timberlake

  11. Atomic Number on the Periodic Table 11 Na Atomic Number Symbol LecturePLUS Timberlake

  12. All atoms of an element have the same number of protons 11 Na 11 protons Sodium LecturePLUS Timberlake

  13. Periodic Table • Represents physical and chemical behavior of elements • Arranges elements by increasing atomic number • Repeats similar properties in columns known as chemical families or groups LecturePLUS Timberlake

  14. Periodic Table 1 2 3 4 5 6 7 8 11 Na LecturePLUS Timberlake

  15. Learning Check State the number of protons for atoms of each of the following: A. Nitrogen 1) 5 protons 2) 7 protons 3) 14 protons B. Sulfur 1) 32 protons 2) 16 protons 3) 6 protons C. Barium 1) 137 protons 2) 81 protons 3) 56 protons LecturePLUS Timberlake

  16. Solution State the number of protons for atoms of each of the following: A. Nitrogen 2) 7 protons B. Sulfur 2) 16 protons C. Barium 3) 56 protons LecturePLUS Timberlake

  17. Number of Electrons • An atom is neutral • The net charge is zero • Number of protons = Number of electrons • Atomic number = Number of electrons LecturePLUS Timberlake

  18. Mass Number Counts the number of protons and neutrons in an atom LecturePLUS Timberlake

  19. Atomic Symbols • Show the mass number and atomic number • Give the symbol of the element mass number 23 Nasodium-23 atomic number11 LecturePLUS Timberlake

  20. Subatomic Particles in Some Atoms 16 31 65 O P Zn 8 15 30 8 p+ 15 p+ 30 p+ 8 n 16 n 35 n 8 e- 15e- 30 e- LecturePLUS Timberlake

  21. Isotopes • Atoms with the same number of protons, but different numbers of neutrons. • Atoms of the same element (same atomic number) with different mass numbers Isotopes of chlorine 35Cl 37Cl 1717 chlorine - 35 chlorine - 37 LecturePLUS Timberlake

  22. Learning Check Naturally occurring carbon consists of three isotopes, 12C, 13C, and 14C. State the number of protons, neutrons, and electrons in each of these carbon atoms. 12C 13C 14C 6 6 6 #p _______ _______ _______ #n _______ _______ _______ #e _______ _______ _______ LecturePLUS Timberlake

  23. Solution 12C 13C 14C 6 6 6 #p 6 6 6 #n 6 7 8 #e 6 6 6 LecturePLUS Timberlake

  24. Learning Check An atom of zinc has a mass number of 65. A. Number of protons in the zinc atom 1) 30 2) 35 3) 65 B. Number of neutrons in the zinc atom 1) 30 2) 35 3) 65 C. What is the mass number of a zinc isotope with 37 neutrons? 1) 37 2) 65 3) 67 LecturePLUS Timberlake

  25. Solution An atom of zinc has a mass number of 65. A. Number of protons in the zinc atom 1) 30 B. Number of neutrons in the zinc atom 2) 35 C. What is the mass number of a zinc isotope with 37 neutrons? 3) 67 LecturePLUS Timberlake

  26. Learning Check Write the atomic symbols for atoms with the following: A. 8 p+, 8 n, 8 e- ___________ B. 17p+, 20n, 17e- ___________ C. 47p+, 60 n, 47 e- ___________ LecturePLUS Timberlake

  27. Solution 16O A. 8 p+, 8 n, 8 e- 8 B. 17p+, 20n, 17e- 37Cl 17 C. 47p+, 60 n, 47 e- 107Ag 47 LecturePLUS Timberlake

  28. Learning Check AT 5 An atom has 14 protons and 20 neutrons. A. Its atomic number is 1) 14 2) 16 3) 34 B. Its mass number is 1) 14 2) 16 3) 34 C. The element is 1) Si 2) Ca 3) Se D. Another isotope of this element is 1)34X 2)34X 3)36X 16 14 14 LecturePLUS Timberlake

  29. Solution AT 5 An atom has 14 protons and 20 neutrons. A. It has atomic number 1) 14 B. It has a mass number of 3) 34 C. The element is 1) Si D. Another isotope of this element would be 3) 36X 14 LecturePLUS Timberlake

  30. Masses of Atoms • A scale designed for atoms gives their small atomic masses in atomic mass units (amu) • An atom of 12C was assigned an exact mass of 12.00 amu • Relative masses of all other atoms was determined by comparing each to the mass of 12C • An atom twice as heavy has a mass of 24.00 amu. An atom half as heavy is 6.00 amu. LecturePLUS Timberlake

  31. Atomic Mass on the Periodic Table 11 Na 22.99 Atomic Number Symbol Atomic Mass LecturePLUS Timberlake

  32. Atomic Mass Na 22.99 • Listed on the periodic table • Gives the mass of “average” atom of each element compared to 12C • Average atom based on all the isotopes and their abundance % • Atomic mass is not a whole number LecturePLUS Timberlake

  33. Atomic Mass Atomic mass is the weighted average mass of all the atomic masses of all the isotopes of that atom. LecturePLUS Timberlake

  34. Weighted Average • You have two types of coins: pennies and quarters.The pennies have a mass of 5g.The quarters  have a mass of 15g.57% of the coins are pennies, 43% of the coins are quarters.What is the average mass of your coins?

  35. Weighted Average – Atomic Mass • You have two isotopes of Boron: 10B and 11B.The 10B has a mass of 10amu.The 11B has a mass of 22 amu.57% of the atoms are 10B, 43% of the atoms are 11B.What is the average mass of your atoms?

  36. Example of an Average Atomic Mass Cl-35 is about 75.5 % and Cl-37 about 24.5% of natural chlorine. 35 x 75.5= 26.4 100 35.5 37 x 24.5= 9.07 100 LecturePLUS Timberlake

  37. Problem AT6 Using the periodic table, specify the atomic mass of each element (round to the tenths place): A. calcium ________ B. aluminum ________ C. lead ________ D. barium ________ E. iron ________ LecturePLUS Timberlake

  38. Solution AT6 Using the periodic table, specify the atomic mass of each element (round to the tenths place): A. calcium _40.1 amu _ B. aluminum _27.0 amu _ C. lead _207.2 amu_ D. barium _137.3 amu_ E. iron _55.8 amu__ LecturePLUS Timberlake

  39. Calculating Atomic Mass Add : Percent (%) abundance of each isotope Multiplied by the Mass of each isotope of that element Weighted average = mass isotope1(%) + mass isotope2(%) + … LecturePLUS Timberlake

  40. Atomic Mass of Magnesium Isotopes Mass of Isotope Abundance 24Mg = 24.0 amu 78.70% 25Mg = 25.0 amu 10.13% 26Mg = 26.0 amu 11.17% Atomic mass (average mass) Mg = 24.3 amu Mg 24.3 LecturePLUS Timberlake

  41. Learning Check AT7 Gallium is a metallic element found in small lasers used in compact disc players. In a sample of gallium, there is 60.2% of gallium-69 (68.9 amu) atoms and 39.8% of gallium-71 (70.9 amu) atoms. What is the atomic mass of gallium? LecturePLUS Timberlake

  42. Solution AT7 Ga-69 68.9 amu x 60.2 = 41.5 amu for 69Ga 100 Ga-71 (%/100) 70.9 amu x 39.8 = 28.2 amu for 71Ga 100 Atomic mass Ga = 69.7 amu LecturePLUS Timberlake

  43. Finding An Isotopic Mass A sample of boron consists of 10B (mass 10.0 amu) and 11B (mass 11.0 amu). If the average atomic mass of B is 10.8 amu, what is the % abundance of each boron isotope? LecturePLUS Timberlake

  44. Assign X and Y values: X = % 10B Y = % 11B Determine Y in terms of X X + Y = 100 Y = 100 - X Solve for X: X (10.0) + (100 - X )(11.0) = 10.8 100 100 Multiply through by 100 10.0 X + 1100 - 11.0X = 1080 LecturePLUS Timberlake

  45. Collect X terms 10.0 X - 11.0 X = 1080 - 1100 - 1.0 X = -20 -1.0 X = -20 -1.0 - 1.0 X = 20 % 10B Y = 100 - X % 11B = 100 - 20% = 80% 11B LecturePLUS Timberlake

  46. Learning Check AT8 Copper has two isotopes 63Cu (62.9 amu) and 65Cu (64.9 amu). What is the % abundance of each isotope? (Hint: Check periodic table for atomic mass) 1) 30% 2) 70% 3) 100% LecturePLUS Timberlake

  47. Solution AT8 2) 70% Solution X + Y = 100 Y = 100 - X Solve for X: X (62.9) + (100 - X )(64.9) = 63.5 100 100 Multiply through by 100 62.9X + 6490 - 64.9X = 6350 -2.0 X = -140 X = 70% LecturePLUS Timberlake

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