Atoms and Subatomic Particles

  • Atomic Theory: All matter exists as atoms, categorized as the smallest particles.

  • Elements: Every atom belongs to a specific element.

  • Common Elements in Living Organisms: Six elements make up the majority of living matter:

    • Oxygen

    • Carbon

    • Hydrogen

    • Nitrogen

    • Calcium

    • Phosphorus

  • Trace Elements: Needed in very small amounts for life (e.g., Iron).

  • Identification: Trace elements can be found on food labels.

Anatomy and Structure of the Atom

  • Subatomic Particles: Composed of protons, neutrons, and electrons.

  • Atomic Regions:

    • Nucleus: Central core of the atom.

    • Electron Cloud: Surrounds the nucleus where electrons reside.

  • Electrical Charges:

    • Opposite charges attract; like charges repel.

  • Protons:

    • Positive charge, determine element identity.

  • Neutrons:

    • Neutral charge, usually equal to protons.

  • Electrons:

    • Negative charge, constantly in motion, attracted to the nucleus.

Atomic Identity: Atomic Number and Isotopes

  • Atomic Number: Total number of protons; characterizes an element.

    • Hydrogen: 1 proton

    • Helium: 2 protons

    • Lithium: 3 protons

  • Isotopes: Atoms of the same element with different neutron counts.

Electron Arrangement and the Octet Rule

  • Bonding Properties: Electrons form chemical bonds, not protons.

  • Orbital Shells: Electrons are arranged in shells around the nucleus.

  • Charge Balancing: Atoms usually have equal protons and electrons.

Chemical Stability and Reactivity

  • Valence Shell: Outermost shell of electrons; maximum stability with full shells.

  • Non-reactive Elements: Full outer shells do not bond (e.g. Neon).

  • Reactive Atoms: Seek bonds to fill outer shells.