AP Chemistry Unit 2.1 Types of Chemical Bonds + Bonding Concepts

Ionic Bonding

Ionic Bonds

• Electrons are transferred from one atom to another creating ions
• Metal + nonmetal
  
  • Metals form cations (lose e- bcuz low IE) and nonmetals form anions (gain e- bcuz high IE)
  • Cations are attracted to anions; (+) & (-) attract
  • Nonmetal achieves electron configuration of next noble gas and valence orbitals of metal are emptied
• Ions are usually more stable than atoms but still unstable because are electrically charged
• Before losing/gaining electrons, atoms are neutral (no charge)
• All elements with more than one charge are metals and give away e- (+)

Types of Ions

• Ions: electrically charged particle

Monatomic = one type of atom (same element)

• H+, \(Ca^2+, N^3-\)

Polyatomic = many types of atoms (different elements) with a charge; small charged molecules

• Held by covalent bonds and net charge is not zero
• Elements are in imperfect bonding → slightly more stable than by itself
  
  • So they are ready to react with a better bond

Lewis Dot Structures

• Valence electrons represented by dots, no more than two per side
• Can show rearrangement of electrons during chemical reactions
• Note:  CH₃⁺→ has lost an e- so C will have only 6 ve-

Binary Ionic Compounds

• Contains ions of only two elements
• Formula: cation first, then anion
  
  • Charges of atoms written as superscript (on top)
  • Number of atoms written as subscripts (on bottom)
  • Cation has positive charge while anion has negative
• The total (net) charge on the compound should be zero

Naming Types of Ionic Compounds

• If cation has more than one valence (can have different charges) indicate the charge using roman numerals in parentheses after the cation name
  
  • FeO = iron (II) Oxide

Binary Ionic Compounds

• Name cation using its element name
  
  • Some have common names (ex. Water, sodium)
• Name anion by dropping ending of the element name and adding -ide
  
  • Ex: Calcium Phosphide → -ide shows that there is one anion

Polyatomic Ionic Compounds

• If anion is polyatomic, name it using the ions name
• Will be polyatomic if ends in -ate or -ite
  
  • -ate = has more oxygen ions
  • -ite = has less oxygen ions
• Treat as one whole unit
• Always use parenthesis () unless there is only one
• Fe(OH)₂
  
  • 3 ions
  • 5 atoms: two subscript belongs to hydrogen AND oxygen

Covalent Bonding

• Covalent Bonds: formed by a share of a pair of electrons between two atoms that completes electron configuration of both atoms
  
  • Between nonmetals (gasses)
• Shared electrons give a lower energy state because they are simultaneously attracted by two nuclei

Types of Covalent Bonds

• Polar covalent bonds = unequal sharing; charges indicated using small delta
  
  • Due to electronegativity difference: electrons pulled to more electroneg. atom
    
    • More electroneg. atom becomes slightly (-) (higher e- density)
    • Less electroneg. atom becomes slightly (+)
  • Soluble in water (hydrophilic) cuz of charge
• Nonpolar covalent bonds = atoms of the same element or with similar electronegativity so have equal sharing of e-
  
  • Ex: O₂, N₂, Cl₂
  • Even though is bonded to itself, is more stable BUT is a strained bond so is ready to react with a better bond
  • No charge

Properties of Covalent Bonds

• Low melting points
  
  • Bcuz attraction between e- are easy to overcome
• Soft, flexible
• Many won’t dissolve/be disrupted in water (nonpolar)
  
  • Cannot conduct electricity even when dissolved bcuz no charges (+ or -) are present
  • Polar covalent can dissolve cuz of charges
• Many are liquids at room temperature
• Flow of electricity:
  
  • NO for nonpolar covalent bonds bcuz e- are tightly held & no charges are present
  • YES for polar covalent bonds in molten form bcuz of charges

Naming Covalent Bonds

• Rule 1: Element with lower group number (more left) goes first
• Rule 2: If elements in same group then greater period number (more down) goes first
• Rule 3: 2nd element in compound ends in -ide
• Use greek prefixes to determine number of atoms

• If there is only one atom of first element, them NO prefix → just elemental name
  
  • Ex CO: Carbon monoxide
• NO CRISS CROSS METHOD