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Chapitre 9
Types de liaisons chimiques
Chemical bonding theories were pioneered by American chemist Gilbert N. Lewis. He developed a model called the Lewis model to explain the type…
Symboles de Lewis et la règle de l'octet
Chemical bonds are complex interactions between two or more atoms or ions, which reduce the potential energy of the molecule. Gilbert N. Lewis…
Liaison ionique et transfert d'électrons
Ions are atoms or molecules bearing an electrical charge. A cation (a positive ion) forms when a neutral atom loses one or more electrons from its…
Le cycle de Born-Haber
An ionic compound is stable because of the electrostatic attraction between its positive and negative ions. The lattice energy of a compound is a…
Tendances de l'énergie réticulaire : taille et charge d'un ion
An ionic compound is stable because of the electrostatic attraction between its positive and negative ions. The lattice energy of a compound is a…
Liaison covalente et structures de Lewis
Compared to ionic bonds, which results from the transfer of electrons between metallic and nonmetallic atoms, covalent bonds result from the mutual…
Électronégativité
Whether a bond is nonpolar or polar covalent is determined by a property of the bonding atoms called electronegativity.  Electronegativity…
Polarisation d'une liaison, moment dipolaire et caractère ionique en pourcentage
The absolute value of the difference in electronegativity (ΔEN) of two bonded atoms provides a rough measure of the polarity to be expected…
Structures de Lewis des composés moléculaires et ions polyatomiques
To draw Lewis structures for complicated molecules and molecular ions, it is helpful to follow a step-by-step procedure as outlined: Determine the…
Résonance
The Lewis structure of a nitrite anion (NO2−) may actually be drawn in two different ways, distinguished by the locations of the N-O and N=O…
Charges formelles
In some cases, there are seemingly more than one valid Lewis structures for molecules and polyatomic ions. The concept of formal charges can be used…
Exceptions à la règle de l'octet
Many covalent molecules have central atoms that do not have eight electrons in their Lewis structures. These molecules fall into three…
Energies de liaison et longueurs de liaison
Stable molecules exist because covalent bonds hold the atoms together. The strength of a covalent bond is measured by the energy required to break…
Liaison dans les métaux
Metallic bonds are formed between two metal atoms. A simplified model to describe metallic bonding has been developed by Paul Drüde called the…
Palladium <em>N</em>-Heterocyclic Carbene Complexes: Synthesis from Benzimidazolium Salts and Catalytic Activity in Carbon-carbon Bond-forming Reactions
Detailed and generalized protocols are presented for the synthesis and subsequent purification of four palladium N-heterocyclic carbene complexes…
Measurement of Ultrafast Vibrational Coherences in Polyatomic Radical Cations with Strong-Field Adiabatic Ionization
We present a pump-probe method for preparing vibrational coherences in polyatomic radical cations and probing their ultrafast dynamics. By shifting…
Preparation of Carbon Nanosheets at Room Temperature
Amphiphilic molecules equipped with a reactive, carbon-rich "oligoyne" segment consisting of conjugated carbon-carbon triple bonds self-assemble into…

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