Unit 1 - Principles of Chemistry: Chapter 7: Ionic Bonding

Compound Formation

• A compound forms when elements chemically combine.

• Ionic compounds form via electron transfer.

Introduction to Ionic Bonding

• Ionic compounds result from metal and non-metal combinations via electron transfer.

• Example: Sodium chloride (NaCl).

• Ionic compounds typically contain a metal and a non-metal.

Learning Objectives

• Understand ion formation.

• Know charges of common ions.

  • Metals (Groups 1, 2, 3): positive ions (cations).

  • Non-metals (Groups 5, 6, 7): negative ions (anions).

  • Specific ions: $Ag^+, Cu^{2+}, Fe^{2+}, Fe^{3+}, Pb^{2+}, Zn^{2+}$

  • Other ions: Hydrogen ($H^+$, Hydroxide ($OH^-$, Ammonium ($NH_4^+$, Carbonate ($CO_3^{2-}$, Nitrate ($NO_3^-$, Sulfate ($SO_4^{2-}$)

• Write formulae for compounds formed between the listed ions.

• Draw dot-and-cross diagrams.

• Understand ionic bonding as electrostatic attractions.

• Understand why giant ionic lattices result in high melting and boiling points.

• Know conductivity in molten or aqueous solution, but not solid.

Ion Formation

• Ions: charged particles formed when atoms lose or gain electrons.

• Cations: positive ions (e.g., $Na^+$).

• Anions: negative ions (e.g., $Cl^-$).

• Electrons transfer from metal to non-metal, creating ions.

• Ionic bonding: electrostatic attraction between ions.

Dot-and-Cross Diagrams

• Represent ionic bonding, showing electron transfer.

• Dots and crosses differentiate electron origins.

Ionic Bonding in Magnesium Oxide (MgO)

• Two electrons transfer from magnesium to oxygen, forming $Mg^{2+}$ and $O^{2-}$.

Noble Gas Electronic Configurations

• Ions often achieve noble gas configurations.

  • Groups 1, 2, 3 lose electrons to form $1^+$, $2^+$, $3^+$ ions.

  • Groups 5, 6, 7 gain electrons to form $3^-$, $2^-$, $1^-$ ions.

Other Examples of Ionic Bonding

• Ionic bonds form when small numbers of electrons (1, 2, or 3) transfer.

Lithium Fluoride (LiF)

• Lithium (Li) loses one electron; fluorine (F) accepts one.

• Forms $Li^+$ and $F^-$ ions.

Calcium Chloride (CaCl₂)

• Calcium (Ca) has two outer electrons; chlorine (Cl) accepts one.

• Two chlorine atoms needed per calcium atom.

• Formula: $CaCl_2$.

Formulae for Ionic Compounds

Determining Ion Charges

• Group 2 elements lose 2 electrons ($2^+$ ions).

• Group 6 elements gain 2 electrons ($2^-$ ions).

• Lead (Pb) forms $Pb^{2+}$.

Cases Where the Name Indicates the Charge

• Names like lead(II) oxide, iron(III) chloride specify charge.

  • lead(II) oxide: $Pb^{2+}$ ions.

  • iron(III) chloride: $Fe^{3+}$ ions.

  • copper(II) sulfate: $Cu^{2+}$ ions.

Ions to Memorize

• Certain ions must be memorized.

Confusing Endings

• "ide": simple compounds (e.g., copper(II) sulfide).

• "ate": presence of oxygen (e.g., copper(II) sulfate).

Deducing the Formula for an Ionic Compound

Example 1: Sodium Oxide

• Sodium (Na): $Na^+$ ions.

• Oxygen (O): $O^{2-}$ ions.

• Formula: $Na_2O$.

Example 2: Barium Nitrate

• Barium (Ba): $Ba^{2+}$ ions.

• Nitrate: $NO_3^-$.

• Formula: $Ba(NO_3)_2$.

Example 3: Iron(III) Sulfate

• Iron(III): $Fe^{3+}$ ions.

• Sulfate: $SO_4^{2-}$.

• Formula: $Fe_2(SO_4)_3$.

Shortcut Method

• Swap the numbers in the charges (cross over method).

• Calcium chloride: $CaCl_2$.

Giant Ionic Structures

• Ionic compounds form lattices of ions.

• Lattice: regular array of particles.

• Held together by electrostatic attractions.

Structure of Sodium Chloride

• Each sodium ion is surrounded by 6 chloride ions, and vice versa.

• Giant ionic lattice structure.

Structure of Magnesium Oxide

• Same structure as NaCl.

• Stronger forces due to $Mg^{2+}$ and $$O^{