4.1: Covalent Bonds

1. To describe how a covalent bond forms.

(资料图)

2. To apply the octet rule to covalent compounds

(Ch. 3 Ionic Bonding)

Electron Sharing

The octet rule

4.2: Covalent Compounds - Formulas and Names

Identify covalent and ionic compounds.

当两种或多种非金属结合时形成"covalent bonds"。

Characteristics of Covalent (Molecular) Compounds: Compounds that contain covalent bonds (also called molecular compounds) exhibit different physical properties than ionic compounds. Because the attraction between molecules, which areelectrically neutral, is weaker than that between electrically charged ions, covalent compounds generally have much lower melting and boiling pointsthan ionic compounds. In fact, many covalent compounds are liquids or gasesat room temperature, and, in their solid states, they are typically much softerthan ionic solids. Furthermore, whereas ionic compounds are good conductors of electricity when dissolved in water, most covalent compounds, being electrically neutral, arepoor conductors of electricity in any state.

4.3: Drawing Lewis Structures

对于非常简单的分子和分子离子，可以通过简单地将组成原子上未成对的电子配对来写出路易斯结构。

对于更复杂的分子和分子离子:

1. Determine the total number of valence (outer shell) electrons among all the atoms.

2. 画出molecule或ion的骨架结构，将原子排列在中心原子周围 (Generally, the least electronegative element should be placed in the center.) Connect each atom to the central atom with a single bond (one electron pair).

3. 将剩余的电子作为lone pairs分布在末端原子（H 除外）上，围绕每个原子完成一个八位组。

4. 将所有剩余的电子放在中心原子上

5. 重新排列外部原子的电子以与中心原子形成多个键，以便尽可能获得octets

/MULTIPLE BONDS: 两个原子共享一对以上的电子才能使两个原子都具有一个八位位组

4.4: Characteristics of Covalent Bonds

Bond Length

nonpolar covalent bond

polar covalent bond

electronegativity

4.5: Characteristics of Molecules

Molecular Shape: VSEPR Theory

Molecular Polarity

4.6: Organic Chemistry

Organic chemistry is the study of the chemistry of carbon compounds.

Carbon is singled out because it has a chemical diversity unrivaled by any other chemical element. Its diversity is based on the following:

Carbon atoms bond reasonably strongly with other carbon atoms.

Carbon atoms bond reasonably strongly with atoms of other elements.

Carbon atoms make a large number of covalent bonds (four).

Alkanes

The simplest organic compounds are the hydrocarbons, compounds composed of carbon and hydrogen atoms only. Some hydrocarbons have only single bonds and appear as a chain (which can be a straight chain or can have branches) of carbon atoms also bonded to hydrogen atoms. These hydrocarbons are called alkanes (saturated hydrocarbons).

烷烃名称: 表示链中碳原子数的词干+ "-ane": 

词干 meth- 表示一个碳原子，甲烷methane是一种具有一个碳原子的烷烃。

词干eth-表示两个碳原子，乙烷ethane是具有两个碳原子的烷烃。

词干 prop- 表示三个碳原子，丙烷propane是具有三个碳原子的烷烃。

词干but-表示四个碳原子，丁烷butane是具有四个碳原子的烷烃。

Alkenes

Some hydrocarbons have one or more carbon–carbon double bonds (denoted C=C). These hydrocarbons are called alkenes.

Alkynes

Alkynes are hydrocarbons with a carbon–carbon triple bond (denoted C≡C) as part of their carbon skeleton.