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Ionic Compounds: Introduction to Bonding

Ionic Compounds: Introduction to Bonding. Bonding: the joining of two atoms in a stable arrangement. Elements will gain , lose , or share electrons to attain the electron configuration of the noble gas closest to them in the periodic table. There are two different kinds of bonding:.

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Ionic Compounds: Introduction to Bonding

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  1. Ionic Compounds: Introduction to Bonding Bonding: the joining of two atoms in a stable arrangement. Elements will gain, lose, or shareelectrons to attain the electron configuration of the noble gas closest to them in the periodic table. There are two different kinds of bonding: • Ionic bonds result from the transfer of electrons • from one element to another. • Covalent bonds result from the sharing of • electrons between two atoms.

  2. During chemical reactions, electrons can be transferred to or from atoms in order to fulfill the octet rule Example: Na  Na+1 + e- Cl + e- Cl-1 Ionic Bond: Attractive force between oppositely charged particles (electrostatic force); results from transfer of electrons between atoms Na+ + Cl- NaCl

  3. Ions: Cations and Anions Cations: positively charged ions (fewer electrons than protons) Anions: negatively charged ions (more electrons than protons)

  4. Some Things to Know About Ionic Compounds: • Metals tend to lose electrons during ionic bond formation • Nonmetals tend to gain electrons during ionic bond formation • No more than 3 electrons are transferred

  5. Metals lose same number of electrons as their group number • Nonmetals gain the number of electrons equal to their group number subracted from 8 (group number - 8) • Examples: Li. (metal, group IA) • Li  Li+ + 1 e- • Cl (nonmetal, group VIIA) • Cl + 1 e- Cl-

  6. Ions Formed by the Main Group Elements

  7. The ratio of positive to negative ions is determined by the charges on the ions (the number of electrons transferred) • The total positive and total negative charges in the final formulas must add up to zero • Example: Na and Cl • Na  Na+ + e- • Cl + 1 e- Cl- • These ions will combine in a 1:1 ratio, to give an ionic compound with a net charge of zero: • NaCl

  8. Example: Mg and F Mg  Mg2+ + 2 e- F + 1 e- F- Mg2+ + F- MgF2 Practice: K and S K  K+ + 1 e- S + 2 e- S2- What is the formula of the ionic compound formed by these 2 ions? K2S

  9. Practice: Ca and Br Ca  Ca2+ + 2 e- Br + 1 e- Br- What is the formula of the ionic compound formed by these 2 ions? Fe+3 + O2- CaBr2 Fe2O3

  10. Ionic compounds exist as crystal structures Crystal lattice: rigid 3-dimensional arrangement of particles

  11. Physical Properties of Ionic Compounds • Ionic compounds have very high melting points (NaCl = 801 oC) • and extremely high boiling points (NaCl = 1413 oC). • When ionic compounds dissolve in water, they separate into cations and anions. The resulting aqueous solutions conduct an electric current. +  solution NaCl water

  12. Naming Ionic Compounds Name of metallic element comes first, followed by stem of nonmetal with the suffix “ide” appended compound name = metal + nonmetal stem + ide Examples: KCl = Potassium chloride SrO = Strontium oxide Ca3N2 = Calcium nitride

  13. Names of Single Ions

  14. Names for individual ions follow the same system (metal name is un-changed, non-metal suffix changes to “ide”) • Example: K+ = Potassium ion • Cl- = Chloride ion • Some atoms (such as the transition metals) can form more than one type of charged ion: • Cu  Cu+ and Cu2+ • Fe  Fe2+ and Fe3+

  15. IonsMetals with Variable Charge 15

  16. Stock System: Uses Roman numeral in name of chemical formula to indicate the charge on metal atom Example: CuCl = Copper(I) chloride CuCl2 = Copper(II) chloride Older system uses suffixes “-ous” and “-ic” attached to root of metal name (uses non-English stem for elements with non-English names) -ous = ion of lower charge -ic = ion of higher charge

  17. Example: Copper (Latin name = cuprum) CuCl = Cuprous chloride CuCl2 = Cupric chloride Example: Iron (Latin name = ferrum) FeCl2 = Ferrous chloride FeCl3 = Ferric chloride

  18. Polyatomic ion: cation or anion that contains more than one atom.

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