Chemistry, like physics, is built upon foundational principles that serve as the basis for understanding the behavior of matter. Here are some key first principles in chemistry:

  1. Law of Conservation of Mass:
    • Mass is neither created nor destroyed in a chemical reaction; it is conserved.
  2. Law of Definite Proportions:
    • A given compound always contains the same elements in the same proportions by mass.
  3. Law of Multiple Proportions:
    • When elements combine to form more than one compound, the ratios of the masses of one element that combine with a fixed mass of another element are in small whole numbers.
  4. Avogadro’s Hypothesis:
    • Equal volumes of gases at the same temperature and pressure contain an equal number of molecules.
  5. Dalton’s Atomic Theory:
    • Elements are composed of atoms.
    • Atoms of different elements have different properties.
    • Compounds are formed by the combination of atoms in simple whole-number ratios.
    • Chemical reactions involve the rearrangement of atoms.
  6. Periodic Law:
    • When elements are arranged in order of increasing atomic number, their properties show a periodic recurrence.
  7. Bohr’s Model of the Atom:
    • Electrons orbit the nucleus in fixed energy levels or shells.
    • Electrons can absorb or emit energy by moving between these energy levels.
  8. Lewis Dot Structures:
    • Representation of the valence electrons of an atom, often used to depict the bonding in molecules.
  9. Octet Rule:
    • Atoms tend to gain, lose, or share electrons to achieve a full set of eight valence electrons.
  10. Electronegativity:
    • The ability of an atom to attract electrons in a chemical bond.
  11. Mole Concept:
    • The mole is a unit for counting atoms and molecules, and it is defined as the amount of substance that contains the same number of entities as there are in 12 grams of carbon-12.
  12. First Law of Thermodynamics:
    • Energy cannot be created or destroyed in a chemical or physical process, but it can change forms.
  13. Second Law of Thermodynamics:
    • The entropy (disorder) of a closed system tends to increase over time.
  14. Gibbs Free Energy:
    • The change in Gibbs free energy determines whether a chemical reaction is spontaneous or non-spontaneous.

These principles provide a framework for understanding the behavior of matter at the atomic and molecular levels and are foundational to the study of chemistry.

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