Writing & Naming Formulas of Ionic & Covalent Compounds

Review of the Periodic Table Periods = number of e- energy levels. Groups (families) = the number of valence electrons (A - groups) IA VIIIA 1 IIA IIIA IVA VA VIA VIIA 2 3 Transition Metals 4 5 6 7

Metals Metalloids Nonmetals Types of Compounds: Ionic = Metal + Nonmetal Covalent = 2 Nometals or Metalloid & Nonmetal Metals Metalloids Nonmetals IA VIIIA IIA IIIA IVA VA VIA VIIA Transition Metals 1 2 3 4 5 6 7 6 7

Eight valence electrons. Chemically stable. Chemical Compounds An atom consist of a positively charged nucleus (protons and neutrons) and orbiting electrons. Very Important! Atoms of elements are not chemically stable until they have 8 valence electrons (octet rule). Atoms gain, lose or share electrons with other atoms to be come chemically stable ( have 8 valence electrons ). -2 Six valence electrons. Not chemically Eight valence electrons. Chemically stable. 8+ 8+ stable. Oxygen Atom Oxide Ion

Two Types of Compounds I o n i c - occurs when a metal loses all its valence electrons to a nonmetal. The metal becomes a cation (+ion), while the nonmetal becomes an anion (- ion). C o v a l e n t - two nonmetals share electrons. Neither loses or gains electrons - they share electrons. Neither atom becomes an ion.

Ionic Compounds Crystalline Lattice

+ + Burning Magnesium 2Mg + O 2 → 2MgO Opposite charges hold the compound together. +2 + -2 + 12+ 8+ 12+ 8+ Magnesium Atom + Oxygen Atom ➝ Magnesium Ion Oxide Ion +

+ + 2Na + Cl 2 → 2NaCl Formation of Sodium Chloride - Opposite charges hold the compound together. - + + + 11+ 17+ 11+ 17+ Sodium Atom Chlorine Atom Sodium Ion Chloride Ion + ➝ +

Ionic Compounds Contain a metal and a nonmetal. The Metal loses e- and becomes a cation (+). The Nonmetal gains e- and becomes an anion(-). Metal is listed first, followed by nonmetal. Change the name of the nonmetal to -ide. Examples: nitride, sulfide, fluoride, oxide, bromide, iodide, chloride, phosphide.

Valence (Oxidation Number) The valence of an elements is the charge an atom takes when it loses or gains electrons and becomes an ion. Metal atoms lose 1, 2 or 3 electrons and become + ions (cations) Nonmetals gain 1,2 or 3 electrons and become - ions (anions) +1 0 +2 +3 -4 -3 -2 -1 Transition Metals Multiple valences

The 5 Steps for writing an ionic compound formula: (1)Write the symbols of the two elements. (2)Write the valence of each as superscripts. (3)Drop the positive and negative signs. (4)Crisscross the superscripts so they become subscripts. (5)Reduce when possible.

Formula for boron oxide 1. Write the symbols of the two elements. B O

Formula for boron oxide 2. Write the valence for each element. +3 -2 B O

Formula for boron oxide 3. Drop the positive & negative sign. -2 3 B O

Formula for boron oxide 4. Crisscross the superscripts so they become subscripts. 3 2 B O

Formula for boron oxide 4. Crisscross the superscripts so they become subscripts. B 2 O 3

Formula for boron oxide 5. Reduce subscripts when possible. (not possible here) B 2 O 3

S r 2O 2 Al 3 P3 Pb2O 4 Ba 3P 2 S r O AlP PbO2 Examples of Reduction of Subscripts: S r 2O 2 Al 3 P3 Pb2O 4 Ba 3P 2 S r O AlP PbO2 Doesn’t Reduce Reduces to Reduces to Reduces to Reduces to 20

Mn+6 Fe+3 Cu+2 Fe+2 Cu+1 Most Transition metals have two valences. Roman numerals are used in the name of the transition metal in the compound to show the valence on the cation. Period 4 Transition Metals Sc TI V Cr Mn Fe Co Ni Cu Zn +3 +4 +5 +6 +2 +1 Examples: Mn+6 Fe+3 Cu+2 Manganese(VI) Iron(III) Copper(II) Mn+4 Manganese(IV) Fe+2 Iron(II) Cu+1 Copper(I) index 21

Examples of Transition Metals Iron(II) Fe +2 Iron(III) Fe +3 Copper(I) Cu+1 Copper(II)Cu+2 Manganese(II) Mn+2 Manganese(IV)Mn+4 index

Naming binary compounds containing a transition metal. Silver(I) chloride Copper(II) phosphide formula Fe2 O3 ZnCl 2 AgCl Cu 3 P2 name Iron(III) oxide Zinc(II) chloride PbS2 MnO2 Lead(IV) sulfide Manganese(IV) oxide

Polyatomic Ions -1 hydroxide Polyatomic (many atom) ions are covalent molecules with a charge. They behave as if they were a one-atom ion.

Polyatomic Ions NH +1 Ammonium Hydroxide NO 2 Nitrite NO 3 Nitrate SO 3 Sulfite SO4 Sulfate CO3 Carbonate PO4 Phosphate -2 4 -1 -2 OH -1 -2 -1 -3 Note: Ammonium is the only polyatomic ion with a + charge. Treat polyatomic ions as you would any ion - crisscross to determine the formula. The only difference is that when you have more than one of a specific polyatomic ion in a formula you must encase it in parenthesis.

Writing Ternary Formulas (Ternary compounds have 3 elements in them.) Cation Anion Compound +2 NO -1 3 Ca(NO3)2 Mg +2 PO -3 4 Mg 3(PO4)2 Ba+2 OH -1 Ba(OH)2 -2 SO4 Ba SO4 Ca As in all ionic compounds you must reduce subscripts, but you cannot change the formula of the polyatomic ion. You can only reduce subscripts outside the parenthesis.

Compounds with Polyatomic ions -2 Carbonate CO 3 Sodium carbonate Na2CO3 Calcium carbonate Ca CO 3 Aluminum carbonate Al2(CO 3)3 Phosphate PO4 -3 Sodium phosphate Na3PO4 Calcium phosphate Ca3(PO3 )2 Aluminum phosphate AlPO3

Covalent Compounds Water Molecule Hydrogen Atom Oxygen Atom

Covalent Compounds Two nonmetals share electrons so both have 8 valence electrons. Exception: H Neither takes on a charge - no valence. Do not crisscross to determine formula. Must use prefixes in the name. Name tells you the formula. Example: N2O4 is dinitrogen tetroxide. You cannot reduce the formulas!!!

+ 2H2 + O2 → 2H2O Reaction between hydrogen + oxygen 1+ 8+ 1+ 1+ 8+ 1+ 1+ 1+ 8+ 1+ 2 Hydrogen Atoms Oxygen Atom Water Molecule

A prefix tells you the number of atoms of that element Covalent Prefixes Mon - 1 Di - 2 Tri - 3 Tetra - 4 Pent - 5 Hex - 6 A prefix tells you the number of atoms of that element in the compound.

N2O3 CH4 PO5 S2F3 Naming Covalent Compounds Dinitrogen trioxide Carbon tetrahydride Phosphorus pentoxide disulfur trifluoride N2O3 CH4 PO5 S2F3

Ionic and Covalent Structure Ionic compounds form a crystalline lattice - a repeating pattern of ions. Water H atoms O atom Covalent compounds form individual molecules that are not connected to each other. +3 B ions N-3 ions Boron nitride

Naming Binary Compounds Does the compound have a metal? Yes No Ionic Covalent (Two Nonmetals) (Metal cation + Nonmetal anion) Place metal first followed by nonmetal ending in -ide Contain a Transition Metal? Place the nonmetal furthest to the left on the periodic table first, then the other nonmetal ending in -ide. Yes Use Roman No Do not use Roman Numerals Examples: sodium chloride magnesium nitride aluminum fluoride beryllium oxide Use prefixes to tell the number of atoms in the compound mon(o)-1, di-2, tri-3, tetr(a)-4, pent(a)-5, hex-6 Examples: dinitrogen trioxide, nitrogen trichloride, phosphorus pentoxide, sulfur dioxide carbon tetrachloride, dihydrogen oxide Numerals to tell the valence of the metal. Examples: iron(III) oxide copper(II) chloride manganese(IV) oxide silver(I) chloride

CoF2 PCl3 Sr3N2 KOH NH3 Name these compounds: cobalt(II) fluoride phorphorus trichloride strontium nitride potassium hydroxide nitrogen trihydride

Zn3N2 LiBr N2O5 MnS2 H2O Write formulas for these compounds: zinc(II) nitride lithium bromide dinitrogen pentoxide manganese(IV) sulfide dihydrogen oxide

Summing up: Ionic Ionic bonding occurs between a metal and a nonmetal. Metals lose all their valence e- and become cations. Nonmetals gain enough e- to fill their valence level and become anions. Always crisscross valences and reduce to determine the formulas of ionic compounds Do not use prefixes in the names. Ions form a crystalline lattice.

Summing up: Covalent Covalent bonding occurs when two nonmetals share electrons to fill their valence energy level. Never use valence to determine the formula - there isn’t any valence. Since the two atoms share electrons, they do not take on a charge. Always use prefixes in the names. Atoms combine to form individual molecules.

Chemical Formulas Index Types of Compounds Ionic Compounds Covalent Compounds Valence Covalent Prefixes Transition Metals Steps in Writing a Formula Polyatomic Ions Lattice & Molecules Naming Flowchart Polar Molecules Summing Up

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