Chemistry: Covalent bond basics Chemistry guide

⚛️ Covalent Bonds: Sharing is Caring!

Covalent bonds are formed when atoms share electrons to achieve a stable electron configuration. This typically occurs between two nonmetal atoms. Unlike ionic bonds where electrons are transferred, covalent bonds involve the mutual sharing of one or more pairs of electrons.

🤝 How Covalent Bonds Form

Atoms form covalent bonds to achieve a full outer electron shell, similar to noble gases. By sharing electrons, both atoms in the bond can effectively 'count' the shared electrons towards their valence shell, leading to increased stability.

Types of Covalent Bonds

• Single Bond: Sharing one pair of electrons (2 electrons). Represented by a single line (-). Example: Hydrogen molecule ($H_2$)
• Double Bond: Sharing two pairs of electrons (4 electrons). Represented by a double line (=). Example: Oxygen molecule ($O_2$)
• Triple Bond: Sharing three pairs of electrons (6 electrons). Represented by a triple line (≡). Example: Nitrogen molecule ($N_2$)

📝 Representing Covalent Bonds: Lewis Structures

Lewis structures are used to visualize covalent bonds and the arrangement of atoms in a molecule. They show how electrons are shared between atoms and any lone pairs (non-bonding pairs) of electrons.

Example: Methane ($CH_4$)

      H
      |
H - C - H
      |
      H

💪 Properties of Covalent Compounds

• Lower Melting and Boiling Points: Compared to ionic compounds, covalent compounds typically have lower melting and boiling points due to weaker intermolecular forces.
• Poor Electrical Conductivity: Covalent compounds generally do not conduct electricity because they lack freely moving ions or electrons.
• Solubility: Solubility varies depending on the polarity of the molecule. Polar covalent compounds tend to dissolve in polar solvents like water, while nonpolar covalent compounds dissolve in nonpolar solvents like hexane.

Polarity in Covalent Bonds ⚡

Covalent bonds can be polar or nonpolar, depending on the electronegativity difference between the bonded atoms.

• Nonpolar Covalent Bond: Electrons are shared equally (electronegativity difference is small or zero). Example: $H_2$
• Polar Covalent Bond: Electrons are shared unequally (significant electronegativity difference). This creates partial charges ($δ+$ and $δ-$) on the atoms. Example: $H_2O$

Example of Polar Covalent Bond in Water ($H_2O$) 💧

Oxygen is more electronegative than hydrogen, so it pulls the shared electrons closer, resulting in a partial negative charge ($δ-$) on oxygen and partial positive charges ($δ+$) on the hydrogen atoms.

      δ+  
      H    
       \  
        O  δ-
       /   
      H    
      δ+