5.2 Ionic and Covalent Bonding

Chemical bonding is the glue that holds atoms together, creating the substances we see every day. In this part, we'll look at two main types of bonds: ionic and covalent. These bonds form differently and give substances unique properties.

Ionic bonds happen when electrons transfer between atoms, while covalent bonds involve sharing electrons. We'll explore how these bonds form, what they look like, and how they affect the stuff around us. Understanding bonds helps us make sense of the world at a tiny level.

Types of Chemical Bonds

Understanding Chemical Bonds and Electronegativity

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• Chemical bonds form strong attractive forces between atoms in molecules or compounds
• Ionic bonds result from electron transfer between atoms with large electronegativity differences
• Covalent bonds involve electron sharing between atoms with similar electronegativity
• Electronegativity measures an atom's ability to attract electrons in a chemical bond
• Electronegativity difference determines the type of bond formed between atoms
  • Large difference (>1.7) typically leads to ionic bonding
  • Small difference (<1.7) usually results in covalent bonding

Characteristics of Ionic and Covalent Bonds

• Ionic bonds form between metals and non-metals (sodium chloride)
• Covalent bonds typically occur between non-metals (water)
• Ionic compounds have high melting and boiling points due to strong electrostatic forces
• Covalent compounds generally have lower melting and boiling points
• Ionic compounds conduct electricity when dissolved or molten
• Most covalent compounds do not conduct electricity

Ionic Bonding

Formation of Ions and Electron Transfer

• Ions form when atoms gain or lose electrons to achieve a stable electron configuration
• Cations are positively charged ions resulting from electron loss (sodium loses one electron)
• Anions are negatively charged ions formed by gaining electrons (chlorine gains one electron)
• Electron transfer occurs from metals to non-metals in ionic bonding
• The number of electrons transferred depends on the valence electrons of each atom

Ionic Compound Properties and Structure

• Ionic compounds consist of repeating units of oppositely charged ions
• Strong electrostatic attractions between ions create a crystalline lattice structure
• Ionic compounds form in whole number ratios to maintain electrical neutrality
• The formula unit represents the simplest whole number ratio of ions in an ionic compound
• Ionic compounds often have high solubility in water due to ion-dipole interactions

Covalent Bonding

Electron Sharing and Lewis Dot Structures

• Covalent bonds involve sharing of electrons between atoms
• Lewis dot structures visually represent valence electrons in covalent molecules
• Dots around element symbols indicate unpaired valence electrons
• Lines between atoms represent shared electron pairs in covalent bonds
• Lewis structures help predict molecular geometry and bond types

Octet Rule and Bond Types

• Octet rule states atoms tend to form bonds to achieve eight valence electrons
• Exceptions to the octet rule include elements in periods 3 and beyond (phosphorus, sulfur)
• Single bonds consist of one shared electron pair between atoms
• Double bonds involve two shared electron pairs (oxygen molecule)
• Triple bonds contain three shared electron pairs (nitrogen molecule)
• Multiple bonds are stronger and shorter than single bonds

Molecular Properties and Polarity

• Covalent molecules can be polar or nonpolar depending on electron distribution
• Polar covalent bonds form when electronegativity difference is between 0.5 and 1.7
• Nonpolar covalent bonds occur when electronegativity difference is less than 0.5
• Molecular polarity affects properties like solubility and boiling point
• Hydrogen bonding, a strong intermolecular force, occurs in molecules with highly electronegative atoms bonded to hydrogen (water)