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Ionic or Molecular

  1. Mar 19, 2006 #1
    How do I determine or predict if a substance is molecular or ionic?

    PLEASE HELP! Thanks!
  2. jcsd
  3. Mar 20, 2006 #2
    Ill try and define some terms.

    A chemical or chemical element that consists of more than one Atom bound together.

    A molecule consisting of a mixture of various different atoms or elements or a larger scale structure formed by multiple combined (chemically bonded) molecules.

    An atom which has a non-neutral charge is called an Ion, they can be positive or negative Ions called Cations and Anions respectivley.

    Refering to a chemical compound (molecule) which consists of atoms that have non-neutral charges. Bonding (thats a model explaining the forces that hold atoms together) in ionic compounds is the result of the attraction between charges ( positive and negative ).

    Having the property of a molecule.

    (a good dictionary should explain these)

    As you can see, Ionic can have the same meaning as molecule, but the converse is not allways so. Some molecules have no Ions in them. It can also be said that in some phases Ionic substances become completeley seperated ( disassociated ) like in solutions or plasmas.
  4. Mar 20, 2006 #3
    Generally, ionic compounds are composed of a metal cation (positive charge) and a nonmetal anion (negative charge). An example is NaCl, which is made up of one Na+ ion and one Cl- ion. Molecular compounds are usually composed of two nonmetals (like CO2).
  5. Mar 20, 2006 #4
    Normally, ionic compounds in aqueous solution dissociate into a cation (positively charged ion) and an anion (negatively charged ion). That's the example of NaCl, mentioned by ksinclair13 and I can give another example as NaHO which dissociates into Na+ and HO- in aqueous solution.
    A molecular substance does not dissociate in aqueous solution, I think.
  6. Mar 20, 2006 #5
    Bonding should clarify this query :wink:

    -Molecular solids are usually held together by (weak) intermolecular forces as hydrogens bonds, dipole-dipole interactions, and dispersion forces. Sucrose (C12H22O11), for example, is a molecular solid, whose strongest intermolecular forces are hydrogen bonds, followed by dipole-dipole interactions, and general dispersion forces.

    -Ionic solids are held together via ionic bonds, often between cations and anions. NaCl is a lattice of sodium cations and chlorine anions held together by ionic bonds (strong electrostatic attractions between ions of opposite charge).
    *Just aside:
    -Network solids are substances held together by strong directional covalent bonds (thus as structural networks of the similar molecules) Usual examples include diamond (held together strong covalent bonds between tetrahedral arrangement of carbods), graphite (layers of sp2-hybridized carbon networks), and quartz (crystalline arrangement of SiO2 molecules held together by covalent bonds with the oxygen atins).
    Last edited: Mar 21, 2006
  7. Mar 21, 2006 #6
    A definition I learned in science yesterday was that ionic compounds are composed of metal and non-matal elements, molecular compounts, also called covalent compounds, are comprised of two or more non-metals.

    Pretty much the same thing ksinclair13 said, just without the cool words :p

    But listen to ksinclair13, he's helepd me out once ;)
  8. Mar 22, 2006 #7
    Actually, it would be wiser to listen to what others have to say because I am very inexperienced. Currently, I'm merely an AP student.

    Hey wScott :-)
  9. Mar 22, 2006 #8
    Me too :smile:
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