3.6: Molecular Compounds - Formulas and Names (2023)

  1. Last update
  2. Save as PDF
  • ID of the page
  • \( \newcommand{\vecs}[1]{\overset { \scriptstyle \rightharpoonup} {\mathbf{#1}}}\) \( \newcommand{\vecd}[1]{\overset{-\!- \!\rightharpoonup}{\vphantom{a}\smash{#1}}} \)\(\newcommand{\id}{\mathrm{id}}\) \( \newcommand{\Span}{\mathrm{ span}}\) \( \newcommand{\kernel}{\mathrm{null}\,}\) \( \newcommand{\range}{\mathrm{range}\,}\) \( \newcommand{\RealPart }{\mathrm{Re}}\) \( \newcommand{\ImaginaryPart}{\mathrm{Im}}\) \( \newcommand{\Argument}{\mathrm{Arg}}\) \( \newcommand{\ norma}[1]{\| #1 \|}\) \( \newcommand{\inner}[2]{\langle #1, #2 \rangle}\) \( \newcommand{\Span}{\mathrm {span}}\) \(\newcommand{\id}{\mathrm{id}}\) \( \newcommand{\Span}{\mathrm{span}}\) \( \newcommand{\kernel}{\ mathrm{null}\,}\) \( \newcommand{\range}{\mathrm{range}\,}\) \( \newcommand{\RealPart}{\mathrm{Re}}\) \( \newcommand{ \ImaginaryPart}{\mathrm{Im}}\) \( \newcommand{\Argumento}{\mathrm{Arg}}\) \( \newcommand{\norm}[1]{\| #1 \|}\) \( \newcommand{\inner}[2]{\langle #1, #2 \rangle}\) \( \newcommand{\Span}{\mathrm{s pan}}\)\( \newcommand{\AA}{\unicode[.8,0]{x212B}}\)

    learning goals

    • Derive names for common types of inorganic compounds using a systematic approach

    The binding properties of inorganic molecular compounds differ from ionic compounds and are also named after a different system. The charges of cations and anions determine their proportions in ionic compounds, so giving ion names provides enough information to determine chemical formulas. However, since covalent bonding allows for considerable variation in the combination ratios of atoms in a molecule, the names of molecular compounds must explicitly indicate these ratios.

    Compounds of two elements

    When two non-metallic elements form a molecular compound, different combination ratios are often possible. For example, carbon and oxygen can form the compounds CO and CO2. Because they are different substances with different properties, they cannot have the same name (they cannot be called carbon oxide). To deal with this situation, we use a naming method somewhat similar to that for ionic compounds, but with additional prefixes to indicate the number of atoms of each element. The name of the most metallic element (the leftmost and/or bottom of the periodic table) comes first, followed by the name of the most nonmetallic element (the rightmost and/or top) with its ending changed to the suffix -Idea. The ordinal numbers of each element are denoted by the Greek prefixes shown in table \(\PageIndex{3}\).

    Table \(\PageIndex{3}\): name prefixes
    Number prefix Number prefix
    1 (sometimes omitted) Mono- 6 Hexa-
    2 Von- 7 Hepta-
    3 tri- 8 Oct-
    4 Tetra- 9 nona-
    5 Five- 10 deka-

    If there is only one atom of the first element, the prefixMono- is usually excluded from this part. Therefore, CO is called carbon monoxide and CO2It's called carbon dioxide. When two vowels are next to each other, theAin the Greek prefix is ​​usually omitted. Some other examples are shown in table \(\PageIndex{4}\).

    (Video) 3.6 Molecular Compounds: Formulas & Names

    Table \(\PageIndex{4}\): Names of some molecular compounds that consist of two elements
    composed Name composed Name
    THEN2 sulfur dioxide BCl3 Bortrichlorid
    THEN3 sulfur trioxide SF6 sulfur hexafluoride
    NO2 nitrogen dioxide PF5 Phosphorpentafluorid
    N2Ö4 nitrous oxide P4Ö10 Tetraphosphordecaoxid
    N2Ö5 nitrous oxide SE7 Iodine Heptafluoride

    There are some common names that you will come across as you continue your study of chemistry. For example, although NO is often referred to as nitric oxide, its real name is nitric oxide. In the same way N2O is known as laughing gas, although our rules call for the name nitrous oxide. (And h2O is usually referred to as water, not dihydrogen monoxide.) You should memorize the common names of compounds as you encounter them.

    Nomenclature of covalent compounds

    Name the following covalent compounds:

    1. SF6
    2. N2Ö3
    3. Kl2Ö7
    4. P4Ö6

    Because these compounds consist only of nonmetals, we use prefixes to denote the number of atoms in each element:

    1. sulfur hexafluoride
    2. nitrous oxide
    3. Dichlorheptoxid
    4. Tetraphosphorhexoxid
    (Video) 3.6 Molecular Compounds: Formulas & Names

    Exercise \(\PageIndex{2}\)

    Write the formulas for the following compounds:

    1. Phosphorpentachlorid
    2. nitrous oxide
    3. Iodine Heptafluoride
    4. Tetrachlorkohlenstoff


    (Video) 3.6 Molecular Compounds: Formulas & Names

    (a) PCl5; (b)N2What? (c) SE7; (d) CCl4

    binary acids

    Some hydrogen-containing compounds belong to an important class of substances known as acids. The chemistry of these compounds will be explored in more detail in later chapters of this text, but for now suffice it to say that many acids liberate hydrogen ions, H+, when dissolved in water. To denote this distinctive chemical property, a mixture of water and an acid is given a name derived from the name of the compound. If the connection abinary acid(composed of hydrogen and another non-metallic element):

    1. The word "hydrogen" is changed to the prefixWater-
    2. The name of the other non-metallic element is modified by adding the suffix -ic
    3. The word “acid” is added as the second word

    For example, when HCl (hydrogen chloride) gas is dissolved in water, the solution is calledhydrochloric acid. Several other examples of this nomenclature are shown in table \(\PageIndex{5}\).

    Table \(\PageIndex{5}\): Names of some simple acids
    Gasname name of the acid
    HF(G), hydrogen fluoride HF(aq), hydrogen sulfide
    HCl(G), hydrogen chloride HCl(aq), hydrochloric acid
    HBr(G), hydrogen bromide HBr(aq), hydrobromic acid
    HEY(G), Jodwasserstoff HEY(aq), iodic acid
    H2S(G), Hydrogensulfat H2S(aq), hydrogen sulfide


    Many compounds that contain three or more elements (e.g. organic compounds or coordination compounds) are subject to special naming rules that you will learn about later. However, let's briefly touch on the important connections known asoxyacids, compounds containing hydrogen, oxygen, and at least one other element, bonded together to give the compound acidic properties (you'll learn the details of this in a later chapter). Typical oxyacids consist of hydrogen combined with a polyatomic ion containing oxygen. To name oxyacids:

    (Video) 3.6 Molecular Compounds: Formulas & Names

    1. Omit "hydrogen".
    2. Start with the root name of the anion
    3. Substitute -he atecom -ic, or -I youcom -us
    4. Add "acid".

    For example, think of H2CO3(which you might be tempted to call "bicarbonate"). To call it right, "hydrogen" is omitted; O -he ateof carbonate is replaced by -ic; and acid is added - hence it is called carbonic acid. You can find more examples in table \(\PageIndex{6}\). There are some exceptions to the general naming method (e.g. H2THEN4is called sulfuric acid, not sulfuric acid, and H2THEN3it is sulphurous, non-sulphurous, acidic).

    Table \(\PageIndex{6}\): Names of common oxyacids
    Formula Name des Anions name of the acid
    CH2H3Ö2 Acetate acetic acid
    HNO3 Nitrate nitric acid
    HNO2 Nitrite nitric acid
    HClO4 perclorato perchloric acid
    H2CO3 Carbonate carbonic acid
    H2THEN4 Sulfate sulfuric acid
    H2THEN3 Sulfites sulphurous acid
    H3AFTER4 phosphate phosphoric acid


    Chemists use naming rules to uniquely name compounds. Ionic and molecular compounds are named using slightly different methods. Binary ionic compounds usually consist of a metal and a nonmetal. The name of the metal is written first, followed by the name of the nonmetal whose suffix is ​​changed to -Idea. For example2That means potassium oxide. When the metal can form ions with different charges, the metal's name is followed by a roman numeral in parentheses, indicating its charge. So, FeCl2is ferrous chloride and FeCl3is ferric chloride. Some compounds contain polyatomic ions; the names of common polyatomic ions must be memorized. Molecular compounds can form compounds with different proportions of their elements, so prefixes are used to indicate the number of atoms of each element in a molecule of the compound. Examples include SF6, sulfur hexafluoride and N2Ö4, nitrous oxide. Acids are an important class of hydrogen-containing compounds with special nomenclature rules. Binary acids are named with the prefixWater-, exchange -IdeaSuffix an -ic, and adding "acid;" HCl is hydrochloric acid. Oxyacids are named by changing the end of the anion to -ic, and adding "acid;" H2CO3it's carbonic.

    employees and tasks


    1. 3.6 Molecular Compounds: Formulas & Names
    (Chemistry with Mrs. K)
    2. 3.6 Molecular Compounds: Formulas & Names
    (Chemistry with Mrs. K)
    3. 3.6 Molecular Compounds: Formulas & Names
    (Chemistry with Mrs. K)
    4. 3.6 Molecular Compounds: Formulas & Names
    (Chemistry with Mrs. K)
    5. 3.6 Molecular Compounds: Formulas & Names
    (Chemistry with Mrs. K)
    6. 3.6 T Molecular Compounds: Formulas & Names
    (Chemistry with Mrs. K)
    Top Articles
    Latest Posts
    Article information

    Author: Greg Kuvalis

    Last Updated: 03/29/2023

    Views: 6154

    Rating: 4.4 / 5 (75 voted)

    Reviews: 82% of readers found this page helpful

    Author information

    Name: Greg Kuvalis

    Birthday: 1996-12-20

    Address: 53157 Trantow Inlet, Townemouth, FL 92564-0267

    Phone: +68218650356656

    Job: IT Representative

    Hobby: Knitting, Amateur radio, Skiing, Running, Mountain biking, Slacklining, Electronics

    Introduction: My name is Greg Kuvalis, I am a witty, spotless, beautiful, charming, delightful, thankful, beautiful person who loves writing and wants to share my knowledge and understanding with you.