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'''Quantum mechanics''' added to [[classical physics]] (in the 1920s) an understanding how particles behave inside [[atom]]s. Quantum mechanics posits that an [[electron]] (or any other [[sub-atomic particle]]) behaves as both a [[wave]] and a [[particle]].
'''Quantum mechanics''' is the branch of [[physics]] that describes the behavior of systems on very small length and energy scales, such as those found in [[atom]]ic and subatomic interactions. It is essential for understanding certain concepts that classical physics cannot explain, such as the discrete nature of small-scale interactions, [[wave-particle duality]], the [[uncertainty principle]], and [[quantum entanglement]]. Quantum mechanics forms the basis for our understanding of many phenomena, including [[chemical reaction]]s and [[radioactive decay]], as well as all computers and electronic devices today.
Quantum mechanics forms the basis for our understanding of chemical reactions, as well as all computers and electronic devices today.
==History==
While the roots of quantum mechanics can be traced to experiments performed in the 19th century, the theory began to emerge when [[Max Planck]] proposed a "quantum hypothesis" to explain the energy spectrum of [[black body]] radiation in 1900. In 1905, [[Albert Einstein]] suggested that light is composed of discrete packets (''quanta'') in order to explain the [[photoelectric effect]]. A decade later, [[Neils Bohr]] proposed a model of the atom in which [[angular momentum is quantized]]. Eventually, the mathematical formalism that became known as quantum mechanics was developed in the 1920s and 1930s, with [[Erwin Schrodinger]]'s discovery of wave mechanics and [[Werner Heisenberg]]'s discovery of matrix mechanics.
==The uncertainty principle==
As a result of the wave nature of the electron, the position of the electron can never be precisely known. Whenever it is attempted to be measured, knowledge of the electron's [[velocity]] is lost. Hence, there is an inherent uncertainty that prevents precisely measuring both the position and the momentum simultaneously. This is known as the [[Heisenberg Uncertainty Principle]].
As a result of the wave nature of the electron, the position of the electron can never be precisely known. Whenever it is attempted to be measured, knowledge of the electron's [[velocity]] is lost. Hence, there is an inherent uncertainty that prevents precisely measuring both the position and the momentum simultaneously. This is known as the [[Heisenberg Uncertainty Principle]].
==Applications==
An important aspect of Quantum Mechanics is the predictions it makes about the [[radioactive decay]] of [[isotopes]]. Radioactive decay processes, controlled by the wave equations, are random events. A radioactive atom has a certain probability of decaying per unit time. As a result, the decay results in an exponential decrease in the amount of isotope remaining in a given sample as a function of time. The characteristic time required for 1/2 of the original amount of isotope to decay is known as the "half-life" and can vary from quadrillionths of a second to quintillions of years.
An important aspect of Quantum Mechanics is the predictions it makes about the [[radioactive decay]] of [[isotopes]]. Radioactive decay processes, controlled by the wave equations, are random events. A radioactive atom has a certain probability of decaying per unit time. As a result, the decay results in an exponential decrease in the amount of isotope remaining in a given sample as a function of time. The characteristic time required for 1/2 of the original amount of isotope to decay is known as the "half-life" and can vary from quadrillionths of a second to quintillions of years.
See:
==See also==
*[[Erwin Schrodinger]], [[Schrodinger equation]]
===Concepts in quantum mechanics===
*[[Schrodinger equation]]
*[[Heisenberg uncertainty principle]]
*[[Heisenberg uncertainty principle]]
*[[Momentum (operator)]]
===Important contributors to quantum mechanics===
*[[Erwin Schrodinger]]
*[[Werner Heisenberg]]
*[[Neils Bohr]]
*[[Albert Einstein]]
*[[Max Planck]]
==External Links==
==External Links==
For an excellent discussion of quantum mechanics, see:
For an excellent discussion of quantum mechanics, see:
http://www.chemistry.ohio-state.edu/betha/qm/
http://www.chemistry.ohio-state.edu/betha/qm/
[[Category:Quantum Mechanics]]
[[Category:Quantum Mechanics]]
[[Category:Physics]]
[[Category:Physics]]