Ionic Compounds Are Composed of What Particles

Ionic Compounds Are Composed of What Particles.

ii.vii: Ions and Ionic Compounds

  • Page ID
    21703
  • Learning Objectives
    • Explicate the bonding nature of ionic compounds.
    • Relating microscopic bonding backdrop to macroscopic solid properties.

    The substances described in the preceding word are composed of molecules that are electrically neutral; that is, the number of positively-charged protons in the nucleus is equal to the number of negatively-charged electrons. In contrast, ions are atoms or assemblies of atoms that accept a net electrical charge. Ions that contain fewer electrons than protons take a cyberspace positive charge and are called cations. Conversely, ions that contain more electrons than protons have a net negative charge and are called anions. Ionic compounds comprise both cations and anions in a ratio that results in no net electric charge.

    In covalent compounds, electrons are shared between bonded atoms and are simultaneously attracted to more than one nucleus. In contrast, ionic compounds comprise cations and anions rather than discrete neutral molecules. Ionic compounds are held together by the attractive electrostatic interactions between cations and anions. In an ionic compound, the cations and anions are arranged in space to grade an extended three-dimensional array that maximizes the number of attractive electrostatic interactions and minimizes the number of repulsive electrostatic interactions (Figure \(\PageIndex{1}\)). As shown in
    Equation \(\ref{Eq1}\), the electrostatic energy of the interaction betwixt two charged particles is proportional to the product of the charges on the particles and inversely proportional to the altitude betwixt them:

    \[ \text {electrostatic free energy} \propto {Q_1Q_2 \over r} \characterization{Eq1} \]

    where \(Q_1\) and \(Q_2\) are the electric charges on particles i and 2, and \(r\) is the altitude betwixt them. When \(Q_1\) and \(Q_2\) are both positive, corresponding to the charges on cations, the cations repel each other and the electrostatic energy is positive. When \(Q_1\) and \(Q_2\) are both negative, corresponding to the charges on anions, the anions repel each other and the electrostatic energy is again positive. The electrostatic energy is negative simply when the charges have contrary signs; that is, positively charged species are attracted to negatively charged species and vice versa.

    Figure \(\PageIndex{1}\): Covalent and Ionic Bonding. (a) In molecular hydrogen (H2), ii hydrogen atoms share 2 electrons to form a covalent bond. (b) The ionic compound NaCl forms when electrons from sodium atoms are transferred to chlorine atoms. The resulting Na+
    and Cl
    ions form a iii-dimensional solid that is held together by attractive electrostatic interactions.
    A: Covalent bonding between two H atoms. B: Ionic bonding between sodium and chlorine, forming a lattice structure.

    Ionic compounds contain both cations and anions in a ratio that results in nada electrical charge.

    Equally shown in
    Figure \(\PageIndex{2}\), the strength of the interaction is proportional to the magnitude of the charges and decreases as the distance between the particles increases. These energetic factors are discussed in greater quantitative detail later.

    Cartoons showing the effect of charge difference and atomic distance on attraction and repulsion.
    Effigy \(\PageIndex{2}\): The Effect of Accuse and Altitude on the Forcefulness of Electrostatic Interactions. Equally the charge on ions increases or the distance between ions decreases, and so does the strength of the attractive (−…+) or repulsive (−…− or +…+) interactions. The strength of these interactions is represented by the thickness of the arrows.

    If the electrostatic energy is positive, the particles repel each other; if the electrostatic free energy is negative, the particles are attracted to each other.

    One instance of an ionic compound is sodium chloride (NaCl;
    Effigy \(\PageIndex{iii}\)), formed from sodium and chlorine. In forming chemical compounds, many elements have a tendency to gain or lose enough electrons to reach the same number of electrons as the noble gas closest to them in the periodic table. When sodium and chlorine come into contact, each sodium atom gives upwardly an electron to become a Na+
    ion, with 11 protons in its nucleus but only 10 electrons (like neon), and each chlorine cantlet gains an electron to become a Cl
    ion, with 17 protons in its nucleus and 18 electrons (like argon), as shown in office (b) in
    Effigy \(\PageIndex{1}\). Solid sodium chloride contains equal numbers of cations (Na+) and anions (Cl), thus maintaining electrical neutrality. Each Na+
    ion is surrounded by 6 Cl
    ions, and each Cl
    ion is surrounded past half dozen Na+
    ions. Because of the large number of bonny Na+Cl
    interactions, the total bonny electrostatic free energy in NaCl is great.

    Cube-like salt crystals. Inset: diagram of N a C l lattice structure.
    Figure \(\PageIndex{3}\): Sodium Chloride: an Ionic Solid. The planes of an NaCl crystal reflect the regular three-dimensional arrangement of its Na+ (purple) and Cl− (dark-green) ions.

    Consistent with a tendency to have the aforementioned number of electrons every bit the nearest noble gas, when forming ions, elements in groups 1, ii, and three tend to lose 1, two, and iii electrons, respectively, to form cations, such as Na+
    and Mg2
    +. They then have the same number of electrons as the nearest noble gas: neon. Similarly, K+, Ca2
    +, and Scthree
    +
    have 18 electrons each, similar the nearest noble gas: argon. In improver, the elements in group xiii lose three electrons to form cations, such as Al3
    +, once again attaining the same number of electrons as the noble gas closest to them in the periodic table. Considering the lanthanides and actinides formally belong to grouping iii, the most mutual ion formed by these elements is M3
    +, where M represents the metal. Conversely, elements in groups 17, 16, and 15 oftentimes react to gain ane, two, and three electrons, respectively, to form ions such as Cl, Southwardtwo−, and P3−. Ions such as these, which incorporate but a single atom, are called monatomic ions. The charges of most monatomic ions derived from the chief group elements tin can exist predicted past simply looking at the periodic tabular array and counting how many columns an element lies from the farthermost left or correct. For example, barium (in Group 2) forms Ba2
    +
    to accept the same number of electrons as its nearest noble gas, xenon; oxygen (in Group 16) forms Oii−
    to take the aforementioned number of electrons every bit neon; and cesium (in Group 1) forms Cs+, which has the same number of electrons every bit xenon. Note that this method is ineffective for most of the transition metals.
    Some common monatomic ions are listed in
    Table \(\PageIndex{1}\).

    Elements in Groups 1, 2, and 3 tend to form 1+, 2+, and 3+ ions, respectively; elements in Groups 15, 16, and 17 tend to class 3−, 2−, and i− ions, respectively.

    Table \(\PageIndex{1}\): Some Common Monatomic Ions and Their Names
    Grouping 1 Group 2 Group three Group xiii Grouping 15 Grouping 16 Group 17
    Li+
    lithium
    Beii
    +
    beryllium
    Niii−
    nitride (azide)
    Oii−
    oxide
    F
    fluoride
    Na+
    sodium
    Mg2
    +
    magnesium
    Aliii
    +
    aluminum
    Piii−
    phosphide
    South2−
    sulfide
    Cl
    chloride
    One thousand+
    potassium
    Ca2
    +
    calcium
    Scthree
    +
    scandium
    Gaiii
    +
    gallium
    Asiii

    arsenide
    Se2

    selenide
    Br
    bromide
    Rb+
    rubidium
    Sr2
    +
    strontium
    Ythree
    +
    yttrium
    In3
    +
    indium
    Te2

    telluride
    I
    iodide
    Cs+
    cesium
    Ba2
    +
    barium
    Lathree
    +
    lanthanum
    Case \(\PageIndex{1}\)

    Predict the charge on the most common monatomic ion formed by each chemical element.

    1. aluminum, used in the quantum logic clock, the earth’s nearly precise clock
    2. selenium, used to make ruby-red-colored glass
    3. yttrium, used to make high-performance spark plugs

    Given: element

    Asked for: ionic charge

    Strategy:

    1. Identify the group in the periodic table to which the element belongs. Based on its location in the periodic tabular array, decide whether the element is a metallic, which tends to lose electrons; a nonmetal, which tends to gain electrons; or a semimetal, which tin practice either.
    2. Later on locating the noble gas that is closest to the element, determine the number of electrons the element must proceeds or lose to have the aforementioned number of electrons as the nearest noble gas.

    Solution:

    1. A
      Aluminum is a metal in grouping 13; consequently, it will tend to lose electrons.
      B
      The nearest noble gas to aluminum is neon. Aluminum will lose three electrons to form the Al3
      +
      ion, which has the aforementioned number of electrons as neon.
    2. A
      Selenium is a nonmetal in group 16, and so it will tend to gain electrons.
      B
      The nearest noble gas is krypton, so we predict that selenium will proceeds two electrons to form the Se2

      ion, which has the same number of electrons as krypton.
    3. A
      Yttrium is in group 3, and elements in this grouping are metals that tend to lose electrons.
      B
      The nearest noble gas to yttrium is krypton, so yttrium is predicted to lose three electrons to form Y3
      +, which has the same number of electrons as krypton.
    Do \(\PageIndex{1}\)

    Predict the charge on the nigh common monatomic ion formed by each chemical element.

    1. calcium, used to prevent osteoporosis
    2. iodine, required for the synthesis of thyroid hormones
    3. zirconium, widely used in nuclear reactors
    Answer a

    Catwo
    +

    Answer b

    I

    Answer c

    Zr4
    +

    Ions of Atoms: Ions of Atoms, YouTube(opens in new window)
    [youtu.be]

    Physical Backdrop of Ionic and Covalent Compounds

    In general, ionic and covalent compounds have unlike physical backdrop. Ionic compounds course hard crystalline solids that melt at high temperatures and are resistant to evaporation. These backdrop stalk from the characteristic internal structure of an ionic solid, illustrated schematically in
    Figure \(\PageIndex{4a}\)
    which shows the three-dimensional assortment of alternating positive and negative ions held together by strong electrostatic attractions. In contrast, as shown in
    Figure \(\PageIndex{4b}\)
    most covalent compounds consist of detached molecules held together by comparatively weak intermolecular forces (the forces betwixt molecules), even though the atoms within each molecule are held together past strong intramolecular covalent bonds (the forces within the molecule).

    Figure \(\PageIndex{4}\): Interactions in Ionic and Covalent Solids. (a) The positively and negatively charged ions in an ionic solid such as sodium chloride (NaCl) are held together by strong electrostatic interactions. (b) In this representation of the packing of marsh gas (\(CH_4\)) molecules in solid methane, a prototypical molecular solid, the methane molecules are held together in the solid only by relatively weak intermolecular forces, even though the atoms within each methyl hydride molecule are held together by strong covalent bonds.
    A: Ionic solid of sodium and chloride ions, showing strong electrostatic interactions. B: Molecular solid consisting of methane, showing weak intermolecular forces.

    Covalent substances tin be gases, liquids, or solids at room temperature and pressure level, depending on the strength of the intermolecular interactions. Covalent molecular solids tend to form soft crystals that cook at low temperatures and evaporate easily. Some covalent substances, however, are not molecular but consist of space three-dimensional arrays of covalently bonded atoms and include some of the hardest materials known, such as diamond. This topic will be addressed elsewhere. The covalent bonds that concord the atoms together in the molecules are unaffected when covalent substances cook or evaporate, so a liquid or vapor of independent molecules is formed. For example, at room temperature, methane, the major elective of natural gas, is a gas that is equanimous of discrete \(\ce{CH4}\) molecules. A comparison of the dissimilar physical properties of ionic compounds and covalent molecular substances is given in
    Table \(\PageIndex{2}\).

    Table \(\PageIndex{ii}\): The Physical Properties of Typical Ionic Compounds and Covalent Molecular Substances
    Ionic Compounds Covalent Molecular Substances
    difficult solids gases, liquids, or soft solids
    high melting points low melting points
    nonvolatile volatile

    Summary

    The atoms in chemic compounds are held together by attractive electrostatic interactions known equally chemic bonds. Ionic compounds contain positively and negatively charged ions in a ratio that results in an overall charge of zero. The ions are held together in a regular spatial arrangement by electrostatic forces. Atoms or groups of atoms that possess a net electrical charge are called ions; they can have either a positive charge (cations) or a negative charge (anions). Ions can consist of one atom (monatomic ions) or several (polyatomic ions). The charges on monatomic ions of most primary group elements tin can be predicted from the location of the chemical element in the periodic table. Ionic compounds usually form hard crystalline solids with high melting points.

    Ionic Compounds Are Composed of What Particles

    Source: https://chem.libretexts.org/Bookshelves/General_Chemistry/Map%3A_Chemistry_-_The_Central_Science_(Brown_et_al.)/02%3A_Atoms_Molecules_and_Ions/2.07%3A_Ions_and_Ionic_Compounds