按照分子轨道理论学说，当成键轨道的电子数目大于反键轨道和非键轨道的电子数目的时候，原子间的共价键的形成是由于电子转入成键的分子轨道的结果。
价键理论和分子轨道理论都是以量子力学的波动方程作为理论依据，它们从不同的角度解释了共价键的本质。
共价键的性质
键能：将以共价键结合的化合物分子（气态）断裂变为原子状态（气态）时所吸收的能量（kJ/mol）
Bond Energy: The energy (kJ/mol) absorbed when a compound molecule (gaseous) bound by a covalent bond breaks into an atomic state (gaseous state).
键长：分子中成键原子的核间距（pm,1pm=10-12m）
Bond length: The nuclear spacing of the bonded atoms in the molecule (pm, 1 pm = 10-12m).
键角：分子中同一原子形成的共价键之间的夹角
Bond angle: The angle between covalent bonds formed by the same atom in a molecule
键的极性（bond polarity）
由于成键原子的电负性不同而引起的，当成键原子的电负性相同时，核间电子云密集区域再两核的中间位置，两个原子核正电荷所形成的正电荷重心和成键电子对的负电荷重心恰好重合，这种性质的共价键称为非极性共价键（nonpolar covalent bond）当成键原子的电负不同时，核间的电子云密集区域偏向电负性较大的原子一端，使之带部分负电荷，二电负性较小的原子一端则带上部分正电荷，键的正电荷中心和负电荷中心不能够发生重合，这样的共价键被称为极性共价键（polar covalent bond）。键的极性大小主要取决于成键原子的电负性的差值，电负性差值越大，键的极性越强。键的极性大小可以用偶极矩来度量偶极矩u=q*d（正电中心或者负电中心上的电荷中心之间的距离d的乘积，称为偶极矩）偶极矩是有方向性的（向量，矢量）
Due to the different electronegativity of the bonded atoms, when the electron negativeity of the bonded atoms is the same, the dense region of the electron cloud between the nuclei is the middle position of the two nuclei, and the positive charge center of gravity formed by the positive charge of the two nuclei coincides with the negative charge center of gravity of the bonded electron pair, and the covalent bond of this property is called thenon-polar covalent bond When the electrons of the bond atoms are different, the dense region of the electron cloud between the nuclei is biased towards the end of the atom with a large negativeity, so that it has a partial negative charge, and the end of the atom with less electronegativity has a partial positive charge, and the positive charge center and the negative charge center of the bond cannot coincide, and such a covalent bond is called a polarcovalent bond. The polarity of the bond mainly depends on the difference in the electronegativity of the bonded atom, and the greater the electronegativity difference, the stronger the polarity of the bond. The polarity of the bond can be measured by the dipole momentu= q * d (the product of the distance d between the centers of charge on the positive or negative center, called the dipole moment) The dipole moment is directional (vector, vector).
键的极化性
分子在外界电场（溶剂、试剂、极性容器等）的影响之下，键的极性会发生一定程度的改变。诱导偶极矩。（类似于软磁体、磁体的磁化）
Under the influence of the external electric field (solvents, reagents, polar containers, etc.), the polarity of the bond will change to a certain extent. Induced dipole moment. (Similar to soft magnets, magnetization of magnets)
共价键的断裂方式以及反应类型
1.共价键均裂
成键的一对电子平均分给两个原子或者原子基团；均裂产生的带电电子的原子或者原子基团，称之为自由基或者游离基团它们是非常活泼的中间体。
2.共价键异裂
成键的一对电子被某一原子或者原子基团所独占。异裂产生正负离子，为较活泼中间体
通过对共价键的断裂方式的学习掌握
1 自由基反应：自由基通常在
光照、加热、自由基引发剂的条件下产生
2 离子型反应异裂。离子型反应一般在酸碱或者极性溶剂催化的条件下进行。分为亲电反应和亲核反应两大类
3 协同反应(周环反应) 旧键断裂和新键形成同时进行。反应过程中，没有活泼中间体自由基生成。一般之共轭烯烃和不饱和烃在加热或者光照的条件下发生的反应，此类反应存在一个环状过渡态，比如双烯合成。
The fracturemode of the covalent bond and the type of reaction
1.The covalent bonds are all cracked
A pair of bondsof electrons is divided equally between two atoms or groups of atoms; atoms orgroups of atoms with charged electrons that are evenly split are called freeradicals or free groups They are very active intermediates.
2.Covalent bonds are heterogeneous
A bonded pairof electrons is monopolized by an atom or group of atoms. Heterocrystalproduces positive and negative ions, which are more active intermediates
Master the wayin which covalent bonds are broken
1 Free RadicalReaction: Free radicals are usually present
Produced underconditions of light, heating, and free radical initiators
2 Ionicreaction heterocraving. Ionic reactions are generally carried out underacid-base or polar solvent-catalyzed conditions. It is divided into two categories:electrophilic reactions and nuclear-friendly reactions
3 Synergisticreaction(cyclic reaction) The old bondbreaks and the new bond formation occurs simultaneously. During the reaction,no active intermediates were produced free radicals. Generally, conjugated andunsaturated hydrocarbons react under heating or light conditions, and suchreactions have a circular transition state, such as diene synthesis.
电子效应
电子效应分为诱导效应和共轭效应
电子效应：电子效应可以用来描述有机化合物分子中原子间相互影响的问题。一定程度上，电子效应解释了有机化合物分子中电子云密度的分布对分子本身性质产生的影响。
诱导效应（I）：由于成键原子的电负性不同，这样会使得整个分子的电子云沿着碳链向某一个方向发生偏移。
诱导效应分为静态诱导效应和动态诱导效应(有外界电场存在)
共轭效应（这一节太难了，没看懂）
有机化合物结构的表示方法
构造式表示：分为电子式、结构式、结构简式、键线式
立体结构的表示方法;楔形式、锯架式、纽曼投影式、费歇尔投影式
有机化合物的分类
按照碳链骨架分类
开链化合物、碳环化合物、杂环化合物
按照官能团分类
双键三键羟基卤素醚基过氧基次卤基氨基亚氨基羟胺基腈基醛基羰基腙基羧基酰基酯基酸酐基胺酰基氰基硝基亚硝基磺酰基
有机化合物研究
分离提纯→实验式和分子式确定→确定结构式
Electroniceffects
Electroneffects are divided into induction effects and conjugate effects
Electroneffects: Electron effects can be used to describe the interaction of atoms inorganic compound molecules. To some extent, the electron effect explains theinfluence of the distribution of electron cloud density in organic compoundmolecules on the properties of the molecule itself.
Induced effect(I): Due to the different electronegativity of bonded atoms, this will causethe electron cloud of the entire molecule to shift along the carbon chain in acertain direction.
The inducedeffect is divided into static induction effect and dynamic induced effect (withthe presence of an external electric field).
Conjugateeffect (this section is too difficult to understand)
Representationof the structure of organic compounds
Constructedform representation: divided into electronic type, structure type, structuresimple type, key line type
Representationof three-dimensional structures; Wedge form, saw frame type, Newman projectiontype, Fisher projection type
Classificationof organic compounds
Classifiedaccording to carbon chain skeleton
Open chaincompounds, carbocyclic compounds, heterocyclic compounds
Classified byfunctional groups
Double bondTribone Hydroxyhalgen Ether PeroxySubhalogen Aminoimino HydroxyminylNitrile Aldehyde Group Carbonyl HydrazylCarboxyl Acyl esteric anhydride amineyl cyanide nitrosonitrosulfonyl
Organiccompound research
Separation andpurification → experimental formula and molecular formula determination→determine the structural formula
