Ionic Bonding Naming Chemical Compounds Chapters 7 and 9

Valence Electrons Elements with similar chemical behavior have the same number of valence electrons. For the representative elements (1A, 2A, 3A, 4A, 5A, 6A, 7A, 8A) the group number corresponds to the number of valence electron in each group (with the exception of He) When examining electron configurations, the electrons that are present in the highest principle energy level represent the valence electrons of those atoms. Br: [Ar]4s 2 3d 10 4p 5 Bromine has 7 valence electrons

Valence Electrons and Electron Dot Structures Valence electrons are the electrons that participate in chemical bonds Electron dot structures consist of the atom symbol and its valence electrons represented as dots. Br: [Ar]4s 2 3d 10 4p 5

The Octet Rule - Metals Metals tend to lose electrons to gain stability. When they lose electrons they attain a stable electron configuration where the next lowest-energy level has a full octet.

The Octet Rule – Non-metals Non-metals tend to gain electrons to obtain a full octet in their highest occupied p sublevel

Formation of Ionic Compounds Cations and anions combine to form ionic compounds + + NaCl

The Formation of Calcium Chloride CaCl 2

Properties of Ionic Compounds The chemical formula for an ionic compound is called a formula unit which represents the lowest who number ration of atoms in that compound ( ex. NaCl) Most ionic compounds are crystalline solids at room temperature Ionic compounds generally have very high melting points Ionic compounds can conduct electricity when molten or dissolved in water Coordination Number = The number of ions of opposite charge surrounding the ion in a crystal.

Metallic Bonding Positive metal ions floating in a sea of electrons. Metals are excellent conductors of electricity Metals can be easily deformed (They are malleable and ductile) Know that metals are arranged in crystalline structures, but do not worry about the arrangement of these structures: face-centered, body- centered, hexagonal.

Alloys Alloys are mixtures of metals Properties of alloys are usually superior to those of their component elements. Substitutional Alloy Interstitial Alloy

Recalling the Periodic Table Metals (Left) Nonmetals (Right) Metalloids (on line) Physical State Reflect light? Malleability/Ductility: hammered/draw to wire? Melting point Conduct heat/electricity? Solid (Except Hg) Solid or Gas (Except Br) Solid Yes. If polished No Some. If polished YesNoSome High Many > 800 o C Low Various YesNoNot well

Periodic Table Review Groups- vertical columns within the periodic table Representative elements- group “A” elements (columns1,2, or s and p block elements) Transition metals- group “B” elements (columns 3-12 or d block elements). Also include inner transition elements or f block elements. Important families of elements Alkali Metals- metals in group 1A that form +1 ions Alkaline Earth Metals- metals in group 2A that form +2 ions Halogens- nonmetals in group 7A that form -1 ions Noble gases- Nonmetals located in far right column that are generally nonreactive

Atoms vs. Ions Atom- NEUTRAL species with equal number of protons and electrons Ion- CHARGED species with unequal number of protons and electrons Cation- (+) ion [lost electron(s)] Anion- (-) ion [gained electron(s)]

Compounds Compound- collection of atoms that is NEUTRAL overall Molecular compound- composed of nonmetals Ionic compound- composed of cations and anions (metal ions and nonmetal ions) in a crystal lattice

Interpreting Chemical Formulas Interpreting Formulas Molecular formula- indicates type and amount of each atom in a compound Diatomic molecules- Br I N Cl H O F exist as two atom molecules when ALONE! (Example: Br 2 ) Formula unit- lowest ratio of ions in an ionic compound (so that charge is zero) Ratio of Atoms in a Compound Law of Definite Proportions Law of Multiple Proportions (Examples: FeCl 2 FeCl 3 )

Writing Formulas of Molecular Compounds Writing Formulas (Example: Carbon Dioxide) More metallic element (or least electronegative)first (Ex: carbon before oxygen) Write symbols for each element next to one another (Ex: CO) Add subscripts to relate number of each atom in the molecule (Ex: CO 2 ) Greek Prefixes- KNOW: mono-, di-, tri-, tetra-, penta-, hexa-, hepta-, octa-, nona-, deca-

Naming Molecular Compounds Naming Binary Molecular Compounds (Ex: SO 3 ) Name in order appearing in formula (Ex: sulfur oxygen) Replace ending of last element with -ide (Ex: sulfur oxide) Add prefixes to indicate number of each atom in molecule (Ex: sulfur trioxide) Note: mono is dropped if there is only one of the first atom. It is used if there is only one of the second atom. (example: CO is named carbon monoxide

Naming Ionic Compounds Most cations are given the element’s name Examples: NaCl = Sodium chloride KCl = Potassium chloride Monatomic anions end in –ide LiBr = Lithium bromide MgS = Magnesium sulfide Polyatomic ions usually end in –ate or –ite Exceptions: OH -1, CN -1, and NH 4 +1

Writing Formulas of Ionic Compounds Writing Formulas of Ionic Compounds (Ex: sodium oxide) Identify charge on metal and nonmetal ions- (Na +1, O 2- ) Criss-cross superscripts to balance charges (Na 2 O) Check if total formula has 0 charge (2 Na +1) + (1 O -2) = 0 Write answer with subscripts (Na 2 O) Note: Polyatomic (many atom) ions are written same except parenthesis are put around them if subscripts are added Example: Magnesium hydroxide (Mg 2+, OH 1- ) = Mg(OH) 2

Stock System- transition metal ion charge Some metals can exist in several forms (Ex: Cu +1, Cu +2 ) Chemical formula used to decide which ion is present (Ex: CuCl 2 – must be Cu +2 ) When naming the ion the charge number is represented in roman numerals in parenthesis following the element name (Ex: copper (II) chloride) ** This is only done for elements that can have more than one possible charge. Refer to your ion table**

Acids Acids- form hydronium ions in water (H 3 O 1+ ) Binary Acids contain H and one non-metal (HCl) The names of binary acids always begin with hydro and are completed by dropping the ending of the nonmetal and adding -ic. HCl = Hydrochloric Acid Oxyacids contain H and a polyatomic anion which contains oxygen Oxyacids are named by dropping the –ate or –ite ending from the anion and adding –ic or –ous. H 2 SO 4 = Hydrogen plus sulfate = sulfuric acid H 2 SO 3 = Hydrogen plus sulfite = sulfurous acid Remember: If you “ate” acid, you might say “ic”!!