Ionic Compounds Chapter 8 I will define a chemical bond I will describe how ions form I will identify ionic bonding and the characteristics of ionic compounds I will name and write chemical formulas for ionic compounds I will relate metallic bonds to the characteristics of metals

Forming Chemical Bonds I will define chemical bond I will relate chemical bond formation to electron configuration I will describe the formation of positive and negative ions Vocabulary: chemical bond, cation, anion

Chemical Bond A force that holds two atoms together Form in two ways: By the attraction between a positive nucleus and negative electrons By the attraction between a positive ion and a negative ion Recall: Valence electrons are involved in the formation of chemical bonds between 2 atoms Atoms want 8 valence electrons so they have a stable electron structure (helium only needs 2)

Formation of Positive Ions Positive ions form when an atom loses one or more valence electrons in order to attain a full outer shell Cation A positively charged ion atom + ionization energy = ion+ + electron(s)

Which Elements Form Positive Ions? Transition Metals (DIFFICULT to predict) Outer energy level ns2 (in general) L R atoms of each element are also filling in the d sublevel Commonly lose their 2 valence electrons (form+2 ions) Also possible for d electrons to be lost Allows them to form +3 ions or greater Group 1A Lose 1 electron Form +1 ions Group 2A Lose 2 electrons Form +2 ions Group 3A (a few) Lose 3 electrons Form +3 ions

Formation of Negative Ions Negative ions form when an atom gains one or more valence electrons in order to attain a full outer shell Anion A negatively charged ion atom + electron(s) = ion-- + electron affinity

Which Elements Form Negative Ions? Nonmetals Gain the number of electrons that when added to their valence electrons, equals 8 The number of electrons gained corresponds to their negative charge Ex gain 2 electrons = form --2 ions To designate an anion, the ending –ide is added to the root name of the element Ex NaCl = sodium chloride Some nonmetals can gain or lose other numbers of electrons to form an octet Ex phosphorous Gain 3 electrons Or Lose 5 electrons MORE LIKELY to GAIN 3!!

Review- Ions that form Look at electron configurations (valence electrons) Metals lose electrons (+ ions) Nonmetals gain electrons (- ions) Typical charges of ions that form

The Formation and Nature of Ionic Bonds I will describe the formation of ionic bonds I will account for many of the physical properties of an ionic compound I will discuss the energy involved in the formation of an ionic bond Vocabulary: ionic bond, electrolyte, lattice energy

Formation of an Ionic Bond The electrostatic force that holds oppositely charged particles together (opposite charge attraction) Ionic Compound Compounds that contain ionic bonds Examples: Oxides Formed if ionic bonds are made between metals and the nonmetal oxygen Salts Most other ionic compounds

Formation of an Ionic Bond Binary Compounds Contain ONLY 2 different elements Contain: Metallic cation Nonmetallic anion Which compound is Binary? MgO CaSO4

Formation of an Ionic Bond The number of electrons lost must EQUAL the number of electrons gained Aka: the overall charge on one unit of the compound must be ZERO Example 1: Na and Cl 1 Na ion (+1) + 1 Cl ion (-1) = (+1) + (-1) = 0 NaCl Example 2: Ca and F 1 Ca ion (+2) + 1 F ion (-1) + 1 F ion (-1) = (+2) + (-1) + (-1) = 0 CaF2

Properties of Ionic Compounds Chemical bonds that occur btwn atoms determine physical properties Ionic compounds (cations + anions) Regular repeating patterns Balance forces of attraction/repulsion Called ionic crystal 1-to-1 ratios of ions produce a cubic crystal Ex. salt

Conductivity Demonstration . Do ionic compounds conduct electricity? ** First…what do you need to conduct electricity?? You need freely moving charged particles. Solid – Aqueous solution – Liquid – do not conduct…why not? do conduct…why? do conduct…why? *** electrolyte: an ionic compound whose aqueous solution conducts an electric current

Properties of Ionic Compounds Crystal Lattice structure – 3D geometric arrangement of ions (positive to negative) Makes them hard – strong bonds Makes them brittle – attracted only to opposite charges/repelled by like charges Have high melting/boiling points

Properties of Ionic Compounds Lattice Energy Energy required to separate 1 mole of ions of an ionic compound Also the energy given off when the ions bond I think of this as “ionic bond energy” – how strong the bond is… *Charge – the larger the charge, the larger the lattice energy Size – the larger the radius, the smaller the lattice energy NaBr, CaCl2, KI, MgO, CaO, BaI2, RbI (rank) RbI < KI < BaI2 < CaCl2 < CaO < MgO RbI = +1, -1 large r + sm charge = smallest LE KI = +1, -1 small r + sm charge = sm LE BaI2 = +2, -2 large r + large charge = med LE CaCl2 = +2, -2 large r + large charge = med LE CaO = +2, -2 large r + large charge = lg LE MgO = +2, -2 large r + large charge = 1g LE

Names and Formulas for Ionic Compounds I will write formulas for ionic compounds and oxyanions I will name ionic compounds and oxyanions Vocabulary: formula unit, monatomic ion, oxidation number, polyatomic ion, oxyanion

Metallic Bonds and Properties of Metals I will describe a metallic bond I will explain the physical properties of metals in terms of metallic bonds I will define and describe alloys Vocabulary: electron sea model, delocalized electrons, metallic bond, alloy