🔗 Covalent Bonds

Understanding covalent bonding and electron sharing

What are Covalent Bonds?

Covalent bonds form when two or more atoms share electrons to achieve a stable electron configuration. This type of bonding typically occurs between nonmetals and results in the formation of molecules.

Main Idea: Covalent bonds involve sharing of electrons between atoms, creating molecules.

How Covalent Bonds Form

Step 1: Electron Sharing

  • • Atoms share valence electrons
  • • Both atoms benefit from sharing
  • • Achieve stable electron configuration

Step 2: Molecular Formation

  • • Shared electrons create bonds
  • • Atoms are held together
  • • Form discrete molecules

Step 3: Stability

  • • Octet rule is satisfied
  • • Lower energy state achieved
  • • Molecule is stable

Example: Hydrogen Molecule (H₂)

Hydrogen Atoms

  • • Each H has 1 valence electron
  • • Need 2 electrons for stability
  • • Share electrons to form H₂
  • • Achieve helium configuration

Covalent Bond

  • • Single covalent bond
  • • 2 shared electrons
  • • Both atoms share equally
  • • Nonpolar covalent bond
H : H or H—H

Two hydrogen atoms share their electrons to form a stable hydrogen molecule.

Types of Covalent Bonds

Single Bonds

One pair of electrons is shared between two atoms.

H—H
H₂ (hydrogen)

Double Bonds

Two pairs of electrons are shared between two atoms.

O=O
O₂ (oxygen)

Triple Bonds

Three pairs of electrons are shared between two atoms.

N≡N
N₂ (nitrogen)

Polar vs Nonpolar Covalent Bonds

Nonpolar Covalent

  • • Equal sharing of electrons
  • • Same or similar electronegativity
  • • No charge separation
  • • Examples: H₂, O₂, N₂

Polar Covalent

  • • Unequal sharing of electrons
  • • Different electronegativities
  • • Partial charge separation
  • • Examples: H₂O, HCl, NH₃

Example: Water (H₂O)

H—O—H

Oxygen is more electronegative than hydrogen, so it attracts electrons more strongly, creating a polar molecule with partial negative charge on oxygen and partial positive charges on hydrogens.

Properties of Covalent Compounds

Lower Melting Points

Weaker intermolecular forces result in lower melting points compared to ionic compounds.

Example: H₂O melts at 0°C

Poor Electrical Conductivity

No free ions or electrons to carry electrical current.

Exception: Some conduct when dissolved

Variable Solubility

Solubility depends on polarity. "Like dissolves like."

Polar dissolves polar, nonpolar dissolves nonpolar

Molecular Structure

Form discrete molecules rather than crystal lattices.

Definite molecular formulas

Soft Solids/Liquids/Gases

Many are gases or liquids at room temperature.

Weak intermolecular forces

Covalent Network

Some form giant covalent networks (diamond, graphite).

Very high melting points

Multiple Bonds and Bond Strength

Bond Strength Increases with Multiple Bonds:

C—C
Single Bond
347 kJ/mol
C=C
Double Bond
614 kJ/mol
C≡C
Triple Bond
839 kJ/mol

Coordinate Covalent Bonds

A coordinate covalent bond (dative bond) forms when one atom provides both electrons for the shared pair. This commonly occurs in Lewis acid-base reactions.

Example: Ammonium Ion (NH₄⁺)

H—N—H

When NH₃ reacts with H⁺, the nitrogen atom donates its lone pair to form a coordinate covalent bond with the hydrogen ion.

Lazy Read

  • • Covalent bonds form through electron sharing between nonmetals
  • • Single, double, and triple bonds involve 1, 2, or 3 shared electron pairs
  • • Nonpolar bonds have equal sharing, polar bonds have unequal sharing
  • • Covalent compounds have lower melting points than ionic compounds
  • • They are poor electrical conductors and form discrete molecules
  • • Multiple bonds are stronger than single bonds
  • • Coordinate covalent bonds involve one atom donating both electrons
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