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4.1.1: Overview of Ionic and Covalent Compounds

  • Page ID
    415125
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    Learning Objectives
    • Classify substances as atomic elements, molecular elements, molecular compounds, or ionic compounds.

    Ionic Compounds

    The elements in the periodic table are divided into specific groupings; the metals, the non-metals, the semi-metals, and so on. These groupings are largely based on physical properties and on the tendency of the various elements to bond with other elements by forming either an ionic or a covalent bond. As a general rule of thumb, compounds that involve a metal binding with either a non-metal or a semi-metal will display ionic bonding. Thus, the compound formed from sodium and chlorine will be ionic (a metal and a non-metal). The basic unit of ionic compounds is the formula unit.

    Covalent (Molecular) Compounds

    Compounds that are composed of only non-metals or semi-metals with non-metals will display covalent bonding and will be classified as molecular compounds. Nitrogen monoxide (NO) will be a covalently bound molecule (two non-metals) and silicon dioxide (SiO2) will also be a covalently bound molecule (a semi-metal and a non-metal). The basic unit of molecular compounds is the molecule.

    Example \(\PageIndex{1}\)

    Provide the classification (i.e. atomic element, molecular element, molecular compound, or ionic compound) of each substance.

    1. Fe
    2. PCl3
    3. LiBr
    4. P4
    5. oxygen gas
    Solution
    1. Fe (iron) is an element that is represented with no subscript, so it is an atomic element.
    2. PCl3 is made up of two nonmetals, so it is a molecular compound.
    3. LiBr is made up of lithium, a metal, and bromine, a nonmetal, so it is an ionic compound.
    4. P4 is a substance that is made up of four atoms of the same element, so it is a molecular element.
    5. The formula for oxygen gas is O2 so it is a molecular element.
    Exercise \(\PageIndex{1}\)

    Provide the classification (i.e. atomic element, molecular element, molecular compound, or ionic compound) of each substance.

    1. I2
    2. He
    3. H2O
    4. Al
    5. CuCl
    Answer a:
    molecular element
    Answer b:
    atomic element
    Answer c:
    molecular compound
    Answer d:
    atomic element
    Answer e:
    ionic compound

    4.1.1: Overview of Ionic and Covalent Compounds is shared under a CK-12 license and was authored, remixed, and/or curated by Marisa Alviar-Agnew & Henry Agnew.

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