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Principal quantum number. In quantum mechanics, the principal quantum number (symbolized n) is one of four quantum numbers assigned to each electron in an atom to describe that electron's state. Its values are natural numbers (from one) making it a discrete variable . Apart from the principal quantum number, the other quantum numbers for bound ...
For example, thallium (Z = 81) has the ground-state configuration 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 10 4p 6 5s 2 4d 10 5p 6 6s 2 4f 14 5d 10 6p 1 or in condensed form, [Xe] 6s 2 4f 14 5d 10 6p 1. Other authors write the subshells outside of the noble gas core in order of increasing n , or if equal, increasing n + l , such as Tl ( Z = 81) [Xe]4f ...
Similarly for organic molecules, the same rule predicts that the first triplet state (denoted by T 1 in photochemistry) is lower than the first excited singlet state (S 1), which is generally correct. However Hund's rules should not be used to order states other than the lowest for a given configuration. For example, the titanium atom ground ...
A measure of disorder in the universe or of the unavailability of the energy in a system to do work. [7] Entropy and disorder also have associations with equilibrium. [8] Technically, entropy, from this perspective, is defined as a thermodynamic property which serves as a measure of how close a system is to equilibrium—that is, to perfect ...
t. e. In quantum physics, a quantum state is a mathematical entity that embodies the knowledge of a quantum system. Quantum mechanics specifies the construction, evolution, and measurement of a quantum state. The result is a quantum-mechanical prediction for the system represented by the state. Knowledge of the quantum state, and the quantum ...
Absolute zero. Zero kelvin (−273.15 °C) is defined as absolute zero. Absolute zero is the lowest limit of the thermodynamic temperature scale; a state at which the enthalpy and entropy of a cooled ideal gas reach their minimum value, taken as zero kelvin. The fundamental particles of nature have minimum vibrational motion, retaining only ...
Magnetic quantum number. In atomic physics, a magnetic quantum number is a quantum number used to distinguish quantum states of an electron or other particle according to its angular momentum along a given axis in space. The orbital magnetic quantum number ( ml or m [a]) distinguishes the orbitals available within a given subshell of an atom.
Term symbol. In atomic physics, a term symbol is an abbreviated description of the total spin and orbital angular momentum quantum numbers of the electrons in a multi-electron atom. So while the word symbol suggests otherwise, it represents an actual value of a physical quantity . For a given electron configuration of an atom, its state depends ...