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The Atom Atomic Number Mass Number Isotopes / Weighted averages Ions Read Chapter 4

The Atom Atomic Number Mass Number Isotopes / Weighted averages Ions Read Chapter 4. Subatomic Particles. Particle Symbol Charge Relative Mass Electron e - -1 0 (negligible) Proton p + + 1 1 Neutron n 0 1. Atomic Number. Represents the number of

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The Atom Atomic Number Mass Number Isotopes / Weighted averages Ions Read Chapter 4

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  1. The Atom Atomic Number Mass Number Isotopes / Weighted averages Ions Read Chapter 4

  2. Subatomic Particles Particle Symbol Charge Relative Mass Electron e- -1 0 (negligible) Proton p+ + 1 1 Neutron n 0 1

  3. Atomic Number Represents the number of protons in an atom- determines identity LecturePLUS Timberlake

  4. Atomic Number on the Periodic Table 11 Na Atomic Number Symbol All atoms of an element have the same number of protons

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

  6. Ions • An ionic particle’s number of electrons differs from the number protons • Results in a net charge. • More electrons than protons creates a negative charge (anion) • Less electrons than protons creates a positive charge (cation) • How many electrons are in the following particles? • Be+2 Br-1 Ga+4

  7. Mass Number Represents the number of protons and neutrons in an atom LecturePLUS Timberlake

  8. Atomic Symbols • Show the mass number and atomic number mass number 23 Nasodium-23 atomic number11 LecturePLUS Timberlake

  9. More Atomic Symbols 16 31 65 O P Zn 8 15 30 LecturePLUS Timberlake

  10. 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

  11. Atomic Mass on the Periodic Table? • Look at the atomic mass for chlorine on the periodic table. How many neutrons do you think it has? • The average atomic mass of an element is the weighted average of the masses of its naturally occurring isotopes. LecturePLUS Timberlake

  12. Weighted Average Problems • The isotopes of chlorine are Cl-35 and Cl-37. In nature 76% of all Cl atoms have a mass of 35 amu (Cl-35) and 24% of all Cl atoms have a mass of 37 amu (Cl-37) LecturePLUS Timberlake

  13. More Weighted Averages Notice that the average atomic mass of an element is close to the mass of the most abundant isotope. The average atomic mass of H is 1.00794 amu and it is calculated from H-1, H-2, and H-3. Which is the most common isotope? LecturePLUS Timberlake

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