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  2. Whole number rule - Wikipedia

    en.wikipedia.org/wiki/Whole_number_rule

    In 1815, William Prout reported on his observation that the atomic weights of the elements were whole multiples of the atomic weight of hydrogen. [7] [8] He then hypothesized that the hydrogen atom was the fundamental object and that the other elements were a combination of different numbers of hydrogen atoms.

  3. Third law of thermodynamics - Wikipedia

    en.wikipedia.org/wiki/Third_law_of_thermodynamics

    Thus S = k ln W = 0. (b) At temperatures greater than absolute zero, multiple microstates are accessible due to atomic vibration (exaggerated in the figure). Since the number of accessible microstates is greater than 1, S = k ln W > 0. The third law provides an absolute reference point for the determination of entropy at any other temperature.

  4. Laws of thermodynamics - Wikipedia

    en.wikipedia.org/wiki/Laws_of_thermodynamics

    [1] [2] [3] A more fundamental statement was later labelled as the zeroth law after the first three laws had been established. The zeroth law of thermodynamics defines thermal equilibrium and forms a basis for the definition of temperature: if two systems are each in thermal equilibrium with a third system, then they are in thermal equilibrium ...

  5. Hund's rules - Wikipedia

    en.wikipedia.org/wiki/Hund's_rules

    We need to consider only the outer 3p 2 electrons, for which it can be shown (see term symbols) that the possible terms allowed by the Pauli exclusion principle are 1 D , 3 P , and 1 S. Hund's first rule now states that the ground state term is 3 P, which has S = 1. The superscript 3 is the value of the multiplicity = 2S + 1 = 3.

  6. Three laws - Wikipedia

    en.wikipedia.org/wiki/Three_laws

    Newton's laws of motion, three physical laws that, together, laid the foundation for classical mechanics; The laws of thermodynamics, originally three physical laws describing thermodynamic systems, though a fourth one was later formulated and is now counted as the zeroth law of thermodynamics

  7. History of atomic theory - Wikipedia

    en.wikipedia.org/wiki/History_of_atomic_theory

    Atomic theory is the scientific theory that matter is composed of particles called atoms. The definition of the word "atom" has changed over the years in response to scientific discoveries. The definition of the word "atom" has changed over the years in response to scientific discoveries.

  8. Raoult's law - Wikipedia

    en.wikipedia.org/wiki/Raoult's_law

    Raoult's law (/ ˈ r ɑː uː l z / law) is a relation of physical chemistry, with implications in thermodynamics.Proposed by French chemist François-Marie Raoult in 1887, [1] [2] it states that the partial pressure of each component of an ideal mixture of liquids is equal to the vapor pressure of the pure component (liquid or solid) multiplied by its mole fraction in the mixture.

  9. Dulong–Petit law - Wikipedia

    en.wikipedia.org/wiki/Dulong–Petit_law

    Molar heat capacity of most elements at 25 °C is in the range between 2.8 R and 3.4 R: Plot as a function of atomic number with a y range from 22.5 to 30 J/mol K.. The Dulong–Petit law, a thermodynamic law proposed by French physicists Pierre Louis Dulong and Alexis Thérèse Petit, states that the classical expression for the molar specific heat capacity of certain chemical elements is ...