Chemical Formulas and Mole Concept

PlantUML Diagram

Chemical Formula and Avogadro's Number

6.3 Chemical Formula and Name of Binary Ionic Compounds

Binary ionic compound: Composed of mono-atomic metal cations and mono-atomic non-metal anions.

Naming convention: Cation name + anion name (with -ide suffix).

Steps to write chemical formula:

  1. Write symbols for cation and anion with charges
  2. Balance charges using smallest coefficients
  3. Write coefficients as subscripts
  4. Omit charge subscripts of 1

Examples:

  • NaCl: Sodium chloride
  • Al₂O₃: Aluminium oxide

6.4 Avogadro's Number and Mole

Mole: Amount of substance containing 6.022 x 1023 particles

Avogadro's number (NA): 6.022 x 1023

Molar mass: Mass of one mole of a substance

6.4.1 Gram Atomic Mass, Gram Molecular Mass, and Gram Formula Mass

Gram atomic mass: Atomic mass of an element expressed in grams

Gram molecular mass: Molecular mass of a substance expressed in grams

Gram formula mass: Formula mass of a substance expressed in grams

Examples:

  • Gram atomic mass of C: 12 g
  • Gram molecular mass of H₂O: 18.016 g
  • Gram formula mass of NaCl: 58.5 g

6.4.2 Differences between Gram Atomic Mass, Gram Molecular Mass, and Gram Formula Mass

Representation:

  • Gram atomic mass: One mole of atoms
  • Gram molecular mass: One mole of molecules
  • Gram formula mass: One mole of ionic formula units

Particle count: All contain 6.022 x 1023 particles

Molar mass: All represent molar mass (mass of one mole of substance in grams)