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In chemistry, sigma bonds (σ bonds) or sigma overlap are the strongest type of covalent chemical bond. [1] They are formed by head-on overlapping between atomic orbitals along the internuclear axis. Sigma bonding is most simply defined for diatomic molecules using the language and tools of symmetry groups. In this formal approach, a σ-bond is ...
The letter Sigma. Sigma (/ ˈ s ɪ ɡ m ə / SIG-mə; [1] uppercase Σ, lowercase σ, lowercase in word-final position ς; Ancient Greek: σίγμα) is the eighteenth letter of the Greek alphabet.
the population mean or expected value in probability and statistics; a measure in measure theory; micro-, an SI prefix denoting 10 −6 (one millionth) Micrometre or micron (retired in 1967 as a standalone symbol, replaced by "μm" using the standard SI meaning) the coefficient of friction in physics; the service rate in queueing theory
What does ‘sigma’ mean? Philip Lindsay, ... “They say, ‘Are you sigma Mr. Lindsay?’ or ‘Yo, that’s so sigma’ when I do something that pleases them like (assigning) math problems ...
Sigma males are “considered ‘equal’ to Alphas on the hierarchy but live outside of the hierarchy by choice,” reads the website. Urban Dictionary adds that sigma “is what all 10 year olds ...
Sigma complexes are of great mechanistic significance, despite their frequent fragility. They represent an initial interaction between the metal center and a hydrocarbon substrate. As such, sigma complexes are generally assumed to be intermediates prior to full oxidative addition .
The triplet and singlet excitation energies of a sigma bond can be used to determine if a bond will follow the homolytic or heterolytic pathway. [2] A metal−metal sigma bond is an exception because the bond's excitation energy is extremely high, thus cannot be used for observation purposes. [2] In some cases, bond cleavage requires catalysts.
Hyperconjugation can be used to rationalize a variety of chemical phenomena, including the anomeric effect, the gauche effect, the rotational barrier of ethane, the beta-silicon effect, the vibrational frequency of exocyclic carbonyl groups, and the relative stability of substituted carbocations and substituted carbon centred radicals, and the thermodynamic Zaitsev's rule for alkene stability.