Origin of quantum number
Words nearby quantum number
How to use quantum number in a sentence
“Our members continue to face a number of challenges,” she said.The Republican War on Kale|Patricia Murphy|January 7, 2015|DAILY BEAST
The number of dissenters though is unprecedented in the modern era.Democrats Accidentally Save Boehner From Republican Coup|Ben Jacobs, Jackie Kucinich|January 6, 2015|DAILY BEAST
Starting under Theodore Roosevelt and Howard Taft, embassies headed by career diplomats increased in number.
The number of diplomats was pitiful (45 appointees in 1860), as was the amount of money allocated to them.
Jett sees this number as a marker of how much the president allows professionals to do the job.
The country is well inhabited, for it contains fifty-one cities, near a hundred walled towns, and a great number of villages.Gulliver's Travels|Jonathan Swift
We had six field-pieces, but we only took four, harnessed wit twice the usual number of horses.
There are a number of bacilli, called acid-fast bacilli, which stain in the same way as the tubercle bacillus.A Manual of Clinical Diagnosis|James Campbell Todd
Five of the number had studied with Liszt before, and the young men are artists already before the public.Music-Study in Germany|Amy Fay
I do not think the average number of passengers on a corresponding route in our country could be so few as twenty.Glances at Europe|Horace Greeley
British Dictionary definitions for quantum number
Scientific definitions for quantum number
A Closer Look
Quantum numbers are used in quantum mechanics to describe the possible states of a physical system. Because many physical properties are quantized, taking on only discrete, distinct values, quantum numbers are generally integers or simple fractions, rather than continuous ranges. One of the great successes of quantum mechanics is its account of the structure of electron orbits around atomic nuclei, and the state of an electron in this particular system can be described using four quantum numbers. These are the principal or first quantum number, the orbital, azimuthal, or second quantum number, the magnetic quantum number, and the spin or spin magnetic quantum number. The principal quantum number, designated n, characterizes the basic energy level for the electron, and indicates in which shell the electron is located. It has integer values starting at 1; the higher the number, the farther the electron is from the atom's nucleus. The principal quantum numbers correspond to the traditional orbital shell designations K, L, M, and so on, used in chemistry. The orbital quantum number, designated l, characterizes the electron's angular momentum and determines the shape of it orbit. Its possible values for a given electron depend on the value of that electron's principal quantum numbers, ranging from 0 to n-1. Because of these different possibilities, shells (other than the first shell) include subshells. These are traditionally designated s (where l=0), p (where l=1), d (where l=2), and f (where l=3). The magnetic quantum number, designated m or ml, takes on integer values between -l and +l, and indicates the orientation of the electron's orbit within the subshell. For example, there are three orbitals in the p subshell, designated as px, py, and pz. Finally, the spin quantum number, designated ms, characterizes the spin direction of the electron. It can have values of + 12 or - 12. Electrons are fermions, meaning that no two electrons can be in the same quantum state (due to the Pauli exclusion principle); therefore, each electron in an atom is uniquely characterized by a set of these four quantum numbers. In fact, the chemical properties of atoms depend almost entirely on the quantum numbers associated with their electrons. Other quantum numbers are used to describe other physical systems, such as the shell structure of the atomic nucleus.