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 Several slides from: stry.com/

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)

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

Which Elements Form Positive Ions? Group 1A Lose 1 electron Form +1 ions Group 2A Lose 2 electrons Form +2 ions Transition Metals (DIFFICULT to predict) Outer energy level ns 2 (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 3A (a few) Lose 3 electrons Form +3 ions

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

Which Elements Form Negative 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!! 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

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 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? MgOCaSO 4

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 CaF 2

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 not conduct…why not? 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 (Exothermic) 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, CaCl 2, KI, MgO, CaO, BaI 2, RbI (rank) RbI < KI < BaI 2 < CaCl 2 < CaO < MgO

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

Names and Formulas of Ionic Compounds A. Formula unit – the simplest ratio of ions in an ionic compound (the formula or “molecule” of an ionic compound) B. Types of ions 1. monatomic ions  one atom makes up the charged particle 2. Polyatomic ions  many atoms make up the charged particle (treat these as units for balancing formulas) C. Oxidation number 1. the charge of the ion (atom) 2. Atoms’ oxidation states add up to the charge of the ion (add up to zero if neutral)

Naming Binary Ionic Compounds Rules The cation (positive ion) is named first, the anion second. Monoatomic cations take the element name. Na +  Sodium Ca 2+  Calcium Monoatomic anions take the elements name and ends with “–ide” Cl -  Chloride Ex NaCl  Sodium Chloride Li 3 N  Lithium Nitride Help

Polyatomic Ions A molecule made up of 2 or more atoms that bears ionic groups (a molecule with a charge) Oxyanions Negative polyatomic ions with oxygen PrefixSuffixExampleNames Per- (more than)-ate (largest #)ClO 4 - perchlorate -ate (large #)ClO 3 - chlorate -ite (smaller #)ClO 2 - chlorite Hypo- (less than)-ite (smallest #)ClO - hypochlorite Help

Naming Compounds with Polyatomic Ions Name the cation (+ion) first (watch for NH 4 + ….ammonium) Name the anion (-ion) second NO prefixes….except dichromate Hydrogen carbonate is also bicarbonate Hydrogen sulfate is also called bisulfate Help

Naming Ionic Compounds using Roman Numerals Naming ionic compounds when the CATION is of variable charge Happens because some elements have more than one oxidation number Roman numeral tells us which oxidation # we have To determine the oxidation # of the cation use your anion Help

Some of the Elements with more than one Oxidation Number

Naming Ionic Compounds using Roman Numerals Example: Pb(NO 3 ) 4 write the name "lead nitrate". Since lead has more than one oxidation state we must figure out which lead we have. Since each nitrate (4 of them) has a 1- charge, the Pb must be 4+. So our roman numeral will be (IV). Pb(NO 3 ) 4 is named "lead(IV) nitrate"

Writing Formulas Identify the symbol of the cation (first part of the name) and the anion Identify the valence or charge of each symbol and place it in parenthesis just above the symbol. silver is 1+, Zinc is 2+ and Aluminum is 3+ Transition elements (have a few charges) will have a Roman Numeral to tell you what positive charge to use

Writing Formulas Balance the total positive and negative charge on the cation and anion. MUST add up to ZERO. If NOT then we ask how many of each ion must we have in order to balance the charge. Once you have determined the number of units of the cation and anion those become the subscripts which are placed right after the respective symbol.

Writing Formulas Ex iron (III) sulfideFe (+3) S (-2) 2Fe ions x (+3) = +6 3S ions x (-2) = -6 Net charge = 0 Formula =Fe 2 S 3

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

Metallic Bonds Metals DO NOT bond ionically DO NOT share or lose electrons to form ions with other metals They DO form crystal lattices (similar to ionic ones) 8-12 other metal atoms surround each metal atom What do metals do??? In their crystal lattice, the outer energy levels of the metal atoms overlap

Metallic Bonds Electron Sea Model All metal atoms in a metallic solid contribute their valence electrons to form a “sea” of electrons forming metallic cations Electrons in outer energy level of bonding metallic atoms are NOT held by any specific atom Electrons can MOVE EASILY from one atom to the next— “delocalized electrons”

Metallic Bonds Metallic Bond Attraction of the metallic cation (metal atom that released its valence electrons to the “sea”) to delocalized electrons (“the sea”) A. Outermost electrons wander freely through metal. Metal consists of cations held together by negatively- charged electron "glue.”

Properties of Metals B. Free electrons can move rapidly in response to electric fields, hence metals are a good conductor of electricity. C. Free electrons can transmit kinetic energy rapidly, hence metals are good conductors of heat. D. The layers of atoms in metal are hard to pull apart because of the electrons holding them together, hence metals are durable (tough). But individual atoms are not held to any other specific atoms, hence atoms slip easily past one another. Thus metals are ductile. (can be drawn into wire)

Properties of Metals Moderately high melting points (vary greatly) Cations and electrons can slide past each other Very high boiling points More extreme-must separate cations from electrons Malleable Can be hammered into sheets Lustrous (shiny) Light reflects off electron sea when polished An applied force causes metal ions to move through delocalized electrons. “layers of atoms slide over each other”

Metal Alloys Alloy A mixture of elements that has metallic properties Properties of an alloy differ somewhat from the properties of the elements they contain Two types: Substitutional Atoms of original metallic solid replaced by other metal atoms of similar size Ex sterling silver, brass, pewter, 10-karat gold Interstitial Formed when small holes in a metallic crystal are filled with smaller atoms (like pouring sand into a bucket of gravel) Ex carbon steel

Metal Alloys