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Ionic vs. molecular
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Ionic vs. molecular

Table of Common Molecular Compounds. These compounds are very common and have names that don't follow the usual naming conventions for molecular compounds. They should be memorized.
Name Formula Name Formula
ammonia NH3 methane CH4
carbon dioxide CO2 nitrous oxide N2O
carbon monoxide CO nitric oxide NO
hydrazine N2H4 sulfur dioxide SO2
hydrogen peroxide H2O2 water H2O
hydrogen sulfide H2S

Ionic compounds

  • definition: Ionic compounds are compounds built from positive ions (cations*) and negative ions (anions*).
  • origin: electron transfer creates anions & cations, which attract because of their opposite charges
Metals are good electron donors, and nonmetals are good electron acceptors.
    Na meets Cl
    electron acceptor (Cl)
    electron donor (Na)
    electron jumps from Na to Cl
    Na+ Cl- ion pair
    ions attract
    to form
    neutral pair
  • structure: smallest building blocks are ions- not molecules!
    • large numbers of ions can attract to form clusters and eventually crystals
      ion pair
      an ion pair
      ion cluster
      an ion cluster
      ion crystal
      an ion crystal
    • ions can separate when compound is dissolved, melted, or vaporized

Comparing ionic and covalent compounds

Quiz Quiz
classifying compounds as ionic or covalent
Table: Comparing ionic and molecular compounds.

Molecular compounds Ionic compounds
smallest particles molecules cations and anions
origin of bonding electron sharing electron transfer
forces between particles strong bonds between atoms
weak attractions between molecules
strong attractions between anions and cations
strong repulsions between ions of like charge
elements present close on the periodic table widely separated on the periodic table
metallic elements present rarely usually
electrical conductivity poor good, when melted or dissolved
state at room temperature solid, liquid, or gas solid
melting and boiling points lower higher
other names covalent compounds salts

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General Chemistry Online! Ionic vs. molecular

Copyright © 1997-2005 by Fred Senese
Comments & questions to fsenese@frostburg.edu
Last Revised 06/11/07.URL: http://antoine.frostburg.edu/chem/senese/101/compounds/ionicvscovalent.shtml