Ch. 7 Ionic Bonds

Chemical Bonds Chemical bonds form when atoms are strongly attracted to one another Ionic Bond Covalent Bond Metallic Bond

Compounds - Review Compound: Substance that is composed of two or more elements that are combined chemically Properties of a compound are generally very different from the elements that make it Chemical Formulas: Formulas show the symbols on the ration of the elements in the compound Subscripts: tell the number of each element in the compound Ex. C12H22O11

Review: Valence Electrons: Electrons in the highest energy level The number of valence electrons largely determines the chemical properties of an element. To find the number of valence electrons, look at its group number. Electron Dot Notation: represents the number of valence electrons

Ions - Review Ion: an atom or bonded group of atoms that has a positive or negative charge When atoms lose electrons and become positive ions, they always become smaller (compared to the neutral atom) Loss of valence electron can leave an empty outer orbital resulting in a small radius When atoms gain electrons and become negative ions, they become larger

Octet Rule Atoms tend to gain, lose (ionic bond) or share (covalent bond) electrons until they are surrounded by eight valence electrons An octet consists of 8 valence electrons Since the noble gases have eight electrons, we assume that an atom is stable when surrounded by 8 valence electrons

A gain of one electron gives chlorine an octet and converts a chlorine atom into a chloride ion. It has the same electron configuration as the noble gas argon.

Ionic Bond Type of chemical bond Electron transfers lead to forces holding atoms together Binds opposite charged ions together Formed by a METAL and a NONMETAL (or a group) Examples: NaCl (Sodium Chloride), Na2CO3 (Sodium Carbonate) **To determine is an element is a metal, nonmetal or metalloid, look at its placement on the periodic table.

Ionic Bonding A bond forms when oppositely charged atoms are electrostatically attracted to one another as a result of the transfer of electrons

Classes of Ionic Bonds Oxides Salts Compounds with ionic bonds between a metal and oxygen Example: MgO (Magnesium Oxide) Salts Generic name for most ionic compounds Examples: NaCl (Sodium Chloride), ZnI2 (Zinc Iodide)

Intro to Ionic Names & Formulas Monatomic Ions: one-atom ions Cation Positive ion formed by the loss of valence electrons Atom loses electrons to have an octet like the previous noble gases Naming: The cation name stays the same as the atom name Example: Li  Lithium Li+  Lithium Ion

Monatomic Ions 2) Anion A Negative ion formed by the gain of electrons Atoms gain electrons to achieve an octet Naming: For the anion, add the suffix –ide to the root of the atom name Example: Br bromine, Br -  Bromide Ion

Oxidation Number (Oxidation State) The charge of a monatomic ion The number of electrons gained or lost to make an ion Monatomic Ion Trends: Group 1: Plus 1 charge Group 2: Plus 2 charge Group 17: Negative 1 charge Group 16: Negative 2 charge Group 15: Negative 3 charge

Practice: Write the symbol, name of the ion, and determine if it’s a cation or anion. An iodine atom gains one electron A strontium atom loses two electrons A sulfur atom gains two electrons An aluminum atom loses three electrons

Practice: Atoms that tend to gain a noble gas configuration by LOSING valence electrons are A. Metals B. Nonmetals C. Noble Gases D. Representative Elements

Polyatomic Ions Polyatomic Ions: Ions made up of more than one atom Charge applies to the whole group Never change the subscripts of atoms within the ion Example: CO32- (Carbonate) Oxyanion: Ion with a nonmetal and one or more oxygen atoms

Polyatomic Ion Trends Naming Element: S Sulfur Anion: S2- Sulfide SO52- Persulfate (+1 oxygen) SO42- Sulfate SO32- Sulfite (-1 oxygen) SO22- Hyposulfite (-2 oxygen)

Ionic Bonds Ion Bond: Metal and Nonmetal Or Positive Ion and Negative Ion When atoms transfer electrons, the atoms become bonded and form ionic compounds Although they are composed of charged ions, ionic compounds are electrically neutral (positive charge = negative charge).

Ionic Nomenclature Writing Ionic Compound Formulas: Write the cation and anion formulas with charges Balance the charges with subscripts if necessary Use parentheses around polyatomic ions that need a subscript added Write the final neutral formula without charges

Practice: Potassium Permanganate: Aluminum Oxide: K+ MnO4-  KMnO4 Aluminum Oxide: Al3+ O2-  add Al3+ Al3+ O2- O2- O2- Al2O3 Copper (II) Hydroxide: Cu2+ OH-  add OH-  Cu(OH)2

More Practice: Sodium Phosphate: Iron (III) Sulfate: Calcium Manganate: Na3PO4 Fe2(SO4)3 CaMnO4

Naming Ionic Compounds Cation name written first Anion name written second **Reminder: Use the roman numerals for most cations

Practice: Li3PO4 -- lithium phosphate Fe(ClO4)2 -- iron (II) perchlorate Na2SO4 – sodium sulfate

More Practice: (NH4)2S AgC2H3O2 CuCl LiHCO3 Ammonium Sulfide Silver Acetate Copper (I) Chloride Lithium Bicarbonate

Properties of Ionic Compounds Crystal Lattice: Ions are arranged in a regular, repeating 3D pattern Each +ion is surrounded by – ions Overall the shape of the crystal depends on the relative number of + ions and – ions

Crystal Structure

Properties of Ionic Compounds Physical Properties: Particles are highly attracted to one another High melting & boiling points Ionic crystals are hard, rigid, and brittle Can conduct electrical currents Electrolyte: an ionic compound whose aqueous solution conducts electricity Aqueous Solutions: A substance dissolved into water