Skip to main content
Chemistry LibreTexts

2: Atoms and the Periodic Table

  • Page ID
    • 2.1: Atomic Theory and the Structure of Atoms
      Atoms are the ultimate building blocks of all matter. The modern atomic theory establishes the concepts of atoms and how they compose matter.
    • 2.2: Elements and Atomic Number
      Atoms are composed of three main subatomic particles: protons, neutrons, and electrons. Protons and neutrons are grouped together in the nucleus of an atom, while electrons orbit about the nucleus.
    • 2.3: Isotopes and Atomic Weight
      Elements can be identified by their atomic number and mass number. Isotopes are atoms of the same element that have different masses.  Atoms have a mass that is based largely on the number of protons and neutrons in their nucleus.
    • 2.4: The Periodic Table
      The chemical elements are arranged in a chart called the periodic table. Some characteristics of the elements are related to their position on the periodic table.
    • 2.5: Some Characteristics of Different Groups
      The periodic table is useful for understanding atomic properties that show periodic trends. Periodic trends are specific patterns that are present in the periodic table that illustrate different aspects of a certain element, including its size and its electronic properties. Periodic trends, arising from the arrangement of the periodic table, provide chemists with an invaluable tool to quickly predict an element's properties.
    • 2.6: Electronic Structure of Atoms
      Electrons in atoms have quantized energies. The state of electrons in atoms is described by four quantum numbers. Electrons are organized into shells and subshells about the nucleus of an atom.
    • 2.7: Electron Configurations
      There are a set of general rules that are used to figure out the electron configuration of an atomic species: Aufbau Principle, Hund's Rule and the Pauli-Exclusion Principle.
    • 2.8: Electron Configurations and the Periodic Table
      The arrangement of electrons in atoms is responsible for the shape of the periodic table. Electron configurations can be predicted by the position of an atom on the periodic table
    • 2.9: Electron-Dot Symbols
      A Lewis electron dot diagram (or electron dot diagram or a Lewis diagram or a Lewis structure) is a representation of the valence electrons of an atom that uses dots around the symbol of the element.

    • Was this article helpful?