Lecture on Atoms and Ions

  • Ion Definition

    • Ion: An electrically charged atom that has gained or lost electrons.
    • Positive ion: More protons than electrons.
    • Negative ion: More electrons than protons.

  • Ion Symbolization

    • Electric charge shown as a superscript in element symbols (e.g., Be$^{2+}$).

  • Ionization Energy

    • Definition: Energy required to remove an electron from a gaseous atom, measured in kJ/mol.
    • Atom’s tendency to hold electrons correlated with ionization energy.
    • First ionization energy: Energy to remove the first electron.
    • Subsequent ionization energies increase for each electron removed.

  • Metals and Nonmetals

    • Metals
    • Properties: Malleable, conduct heat, low ionization energy.
    • Tend to lose electrons, forming positive ions.
    • Nonmetals
    • Properties: Poor conductors, high ionization energy.
    • Tend to gain electrons, forming negative ions.

  • Nucleus

    • Definition: Positively charged, dense central core of an atom.
    • Contains protons and neutrons, accounting for over 99.9% of atomic mass, but occupies only 1/100,000 of the atom's volume.

  • Periodic Table Concepts

    • Period: Horizontal row in the periodic table, with elements having the same number of energy levels.
    • Periodic Trend: Predictable pattern (e.g., atomic radius, ionization energy) within a period.
    • Picometer: Unit of length for measuring atomic radius (1 picometer = $10^{-12}$ meters).

  • Valence Electron

    • Definition: Electron found in the outermost energy level.