Fundamental principles in Chemistry

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.