4.1: Covalent Bonds

1. To describe how a covalent bond forms.

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.

當兩種或多種非金屬結合時形成"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 are electrically neutral, is weaker than that between electrically charged ions, covalent compounds generally have much lower melting and boiling points than ionic compounds. In fact, many covalent compounds are liquids or gases at room temperature, and, in their solid states, they are typically much softer than ionic solids. Furthermore, whereas ionic compounds are good conductors of electricity when dissolved in water, most covalent compounds, being electrically neutral, are poor conductors of electricity in any state.

4.3: Drawing Lewis Structures

對于非常簡單的分子和分子離子，可以通過簡單地將組成原子上未成對的電子配對來寫出路易斯結構。

對于更復雜的分子和分子離子:

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

2. 畫出molecule或ion的骨架結構，將原子排列在中心原子周圍?(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. 將剩余的電子作為lone pairs分布在末端原子（H 除外）上，圍繞每個原子完成一個八位組。

4. 將所有剩余的電子放在中心原子上

5. 重新排列外部原子的電子以與中心原子形成多個鍵，以便盡可能獲得octets

/MULTIPLE BONDS: 兩個原子共享一對以上的電子才能使兩個原子都具有一個八位位組

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).

烷烴名稱:?表示鏈中碳原子數(shù)的詞干+?"-ane":?

詞干 meth- 表示一個碳原子，甲烷methane是一種具有一個碳原子的烷烴。

詞干eth-表示兩個碳原子，乙烷ethane是具有兩個碳原子的烷烴。

詞干 prop- 表示三個碳原子，丙烷propane是具有三個碳原子的烷烴。

詞干but-表示四個碳原子，丁烷butane是具有四個碳原子的烷烴。

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.?