Properties of water:

Atoms: The Basic Units of Chemical Elements

• Atoms are the fundamental building blocks of matter and represent the smallest unit of chemical elements.

Subatomic Particles in Atoms

• Each atom consists of subatomic particles located in two main regions:

  • Nucleus: Contains

    • Protons: Positively charged particles (+).

    • Neutrons: Uncharged particles (neutral).

  • Electron Cloud: Surrounds the nucleus and contains

    • Electrons: Negatively charged particles (–).

• Atoms are electrically neutral because they have an equal number of protons and electrons.

Example: Carbon Atom

• A model of carbon:

  • Contains 6 protons, 6 electrons, and typically 6 neutrons.

  • Electrons are arranged in shells around the nucleus.

  • Each shell corresponds to a different energy level and has a maximum number of electrons it can hold.

Stability in Electron Shells

• Outer electrons (valence electrons) are involved in chemical bonding during reactions.

• Atoms with a single energy level (1 shell):

  • Helium: 2 electrons (full shell) - stable, no compounds found in nature.

  • Hydrogen: 1 electron (not full shell) - chemically reactive.

• Atoms with multiple energy levels:

  • Stability Rule: 8 electrons in the outermost shell are required for stability (octet rule).

  • Neon: 8 electrons in the outermost shell - stable.

  • Oxygen: 6 electrons in the outermost shell - chemically reactive.

Octet Rule and Chemical Reactivity

• Atoms with fewer than 8 electrons in their outermost shell will:

  • Attempt to share, gain, or lose electrons to achieve a stable configuration.

• The octet rule explains the reactivity of atoms except for those like hydrogen and helium, which have differing requirements due to their single shell.

Conclusion

• Understanding atomic structure and electron configuration is essential for grasping the principles of chemical reactions and stability.