Chapter 6 Chemical Names and Formulas

Section 6.1 Introduction to Chemical Bonding OBJECTIVES: Distinguish between ionic and molecular compounds.

Section 6.1 Introduction to Chemical Bonding OBJECTIVES: Define cation and anion, and relate them to metal and nonmetal.

Molecules and Molecular Compounds About 100 different elements Millions of compounds from them Naming is essential in chemistry Noble gases, such as He and Ne Isolated atoms- monatomic, they consist of single atoms

Molecules and Molecular Compounds Molecule- smallest electrically neutral unit, still has properties of the substance Made from only nonmetals Can be from one element- O2 Can make a compound- CO2

Molecules and Molecular Compounds Properties of molecular compounds Low melting and boiling points Usually gas or liquid Composed of two or more nonmetals O2, O3, H2O

Systematic Naming There are too many compounds to remember the names of them all. Compound is made of two or more elements. Put together atoms. Name should tell us how many and what type of atoms.

Atoms and ions Atoms are electrically neutral. Same number of protons and electrons. Ions are atoms, or groups of atoms, with a charge (positive or negative) Different numbers of protons and electrons. Only electrons can move. Gain or lose electrons.

F- O2- Anion A negative ion. Has gained electrons. Nonmetals can gain electrons. Charge is written as a superscript on the right. Has gained one electron (-ide is new ending= fluoride) F- O2- Gained two electrons (oxide)

K+ Ca2+ Cations Positive ions. Formed by losing electrons. More protons than electrons. Metals can lose electrons K+ Has lost one electron (no name change for positive ions) Ca2+ Has lost two electrons

Ionic Compounds Ionic compounds- from joining metal cations and nonmetal anions- they are electrically neutral Usually solid crystals Melt at high temperatures

Two Types of Compounds Molecular compounds Made of molecules. Made by joining nonmetal atoms together into molecules.

Two Types of Compounds Ionic Compounds Made of cations and anions. Metals and nonmetals. The electrons lost by the cation are gained by the anion. The cation and anions surround each other. Smallest piece is a FORMULA UNIT.

Two Types of Compounds Ionic Molecular Smallest piece Formula Unit Molecule Types of elements Metal and Nonmetal Nonmetals Solid, liquid or gas State solid Melting Point High >300ºC Low <300ºC

Section 6.2 Representing Chemical Compounds OBJECTIVES: Distinguish among chemical formulas, molecular formulas, and formula units.

Section 6.2 Representing Chemical Compounds OBJECTIVES: Use experimental data to show that a compound obeys the law of definite proportions.

Chemical Formulas Shows the kind and number of atoms in the smallest piece of a substance. Molecular formula- number and kinds of atoms in a molecule. CO2 C6H12O6

Chemical Formulas More than one atom? –use a subscript (H2O) There are 7 diatomic elements Hydrogen (H2), Nitrogen (N2), Oxygen (O2), Fluorine (F2), Chlorine (Cl2), Bromine (Br2), and Iodine (I2) Remember: “Br I N Cl H O F”

Ionic Compounds This formula represents not a molecule, but a formula unit The smallest whole number ratio of atoms in an ionic compound. Ions surround each other so you can’t say which is hooked to which. (p. 140)

Some Laws: 1. Law of Definite Proportions- in a sample of a chemical compound, the masses of the elements are always in the same proportions. H2O (water) and H2O2 (hydrogen peroxide)

Some Laws: 2. Law of Multiple Proportions- Dalton stated that whenever two elements form more than one compound, the different masses of one element that combine with the same mass of the other element are in the ratio of small whole numbers. Figure 6.11, p. 141

Section 6.3 Ionic Charges OBJECTIVES: Use the periodic table to determine the charge on an ion.

Section 6.3 Ionic Charges OBJECTIVES: Define a polyatomic ion, and give the names and formulas of the most common polyatomic ions.

Charges on ions For most of the Group A elements, the Periodic Table can tell what kind of ion they will form from their location; monatomic ions Elements in the same group have similar properties. Including the charge when they are ions.

1+ 2+ 3+ 3- 2- 1-

What about the others? Groups 4A and 0 do not usually form ions (in fact, Group 0 rarely forms compounds!) Many transition metals have more than one common ionic charge

Naming ions Two methods if more than one charge is possible: 1. Stock system – uses roman numerals in parenthesis to indicate the numerical value 2. Classical method – uses root word with suffixes (-ous, -ic) Does not give true value

Naming ions We will use the Stock system. Cation- if the charge is always the same (Group A) just write the name of the metal. Transition metals can have more than one type of charge. Indicate the charge with roman numerals in parenthesis (Table 6.3, p.144)

Name these Na+ Ca2+ Al3+ Fe3+ Fe2+ Pb2+ Li+

Write Formulas for these Potassium ion Magnesium ion Copper (II) ion Chromium (VI) ion Barium ion Mercury (II) ion

Naming Anions Anions are always the same charge Change the element ending to – ide F- Fluorine

Naming Anions Anions are always the same charge Change the element ending to – ide F- Fluorin

Naming Anions Anions are always the same charge Change the element ending to – ide F- Fluori

Naming Anions Anions are always the same charge Change the element ending to – ide F- Fluor

Naming Anions Anions are always the same charge Change the element ending to – ide F- Fluori

Naming Anions Anions are always the same charge Change the element ending to – ide F- Fluorid

Naming Anions Anions are always the same charge Change the element ending to – ide F- Fluoride

Name these Cl- N3- Br- O2- Ga3+

Write these Sulfide ion iodide ion phosphide ion Strontium ion

Exceptions: Some of the transition metals have only one ionic charge: Do not use roman numerals for these: Silver is always 1+ (Ag+) Cadmium and Zinc are always 2+ (Cd2+ and Zn2+) Note Fig. 6.13, p. 145

Polyatomic ions Groups of atoms that stay together and have a charge. Learn these - Table 6.4, p.147 Acetate C2H3O2- Nitrate NO3- Nitrite NO2- Hydroxide OH- and Cyanide CN- Permanganate MnO4-

Polyatomic ions Sulfate SO42- Sulfite SO32- Carbonate CO32- Chromate CrO42- Dichromate Cr2O72- Phosphate PO43- Phosphite PO33- Ammonium NH4+

Section 6.4 Ionic Compounds OBJECTIVES: Apply the rules for naming and writing formulas for binary ionic compounds.

Section 6.4 Ionic Compounds OBJECTIVES: Apply the rules for naming and writing formulas for ternary ionic compounds.

Naming Binary Ionic Compounds Binary Compounds - 2 elements. Ionic - a cation and an anion. To write the names, just name the two ions. Easy with Representative elements (which are Group A elements) NaCl = Na+ Cl- = sodium chloride MgBr2 = Mg2+ Br- = magnesium bromide

Naming Binary Ionic Compounds The problem comes with the transition metals. Need to figure out their charges. The compound must be neutral. same number of + and – charges. Use the anion to determine the charge on the positive ion.

Naming Binary Ionic Compounds Write the name of CuO Need the charge of Cu O is 2- copper must be 2+ Copper (II) oxide Name CoCl3 Cl is 1- and there are three of them = 3- Co must be 3+ Cobalt (III) chloride

Naming Binary Ionic Compounds Write the name of Cu2S. Since S is 2-, the Cu2 must be 2+, so each one is 1+. copper (I) sulfide Fe2O3 Each O is 2- 3 x -2 = -6 2 Fe must = 6+, so each is 3+. iron (III) oxide

Naming Binary Ionic Compounds Write the names of the following KCl Na3N CrN Sc3P2 PbO PbO2 Na2Se

Ternary Ionic Compounds These will have polyatomic ions At least three elements name the ions NaNO3 CaSO4 CuSO3 (NH4)2O

Ternary Ionic Compounds LiCN Fe(OH)3 (NH4)2CO3 NiPO4

Writing Formulas The charges have to add up to zero. Get charges on pieces. Cations from name on table. Anions from table or polyatomic. Balance the charges by adding subscripts. Put polyatomics in parenthesis.

Writing Formulas Write the formula for calcium chloride. Calcium is Ca2+ Chloride is Cl- Ca2+ Cl- would have a 1+ charge. Need another Cl- Ca2+ Cl21- (use criss-cross method)

Write the formulas for these Lithium sulfide tin (II) oxide tin (IV) oxide Magnesium fluoride Copper (II) sulfate Iron (III) phosphide gallium nitrate Iron (III) sulfide

Write the formulas for these Ammonium chloride ammonium sulfide barium nitrate

Things to look for If cations have ( ), the number in parenthesis is their charge. If anions end in -ide they are probably off the periodic table (Monoatomic) If anion ends in -ate or -ite it is polyatomic

Section 6.5 Molecular Compounds and Acids OBJECTIVES: Apply the rules for naming and writing formulas for binary molecular compounds.

Section 6.5 Molecular Compounds and Acids OBJECTIVES: Name and write formulas for common acids.

Molecular compounds made of just nonmetals smallest piece is a molecule can’t be held together because of opposite charges. can’t use charges to figure out how many of each atom

Molecular are easier! Ionic compounds use charges to determine how many of each. Have to figure out charges. Have to figure out numbers. Molecular compounds name tells you the number of atoms. Uses prefixes to tell you the number

Prefixes (Table 6.5, p.159) 1 = mono- 2 = di- 3 = tri- 4 = tetra- 5 = penta- 6 = hexa- 7 = hepta- 8 = octa-

Prefixes 9 = nona- 10 = deca- To write the name, write two words:

Prefixes Prefix name Prefix name -ide 9 = nona- 10 = deca- To write the name, write two words: Prefix name Prefix name -ide

Prefixes Prefix name Prefix name -ide 9 = nona- 10 = deca- To write the name, write two words: One exception is we don’t write mono- if there is only one of the first element. Prefix name Prefix name -ide

Prefixes Prefix name Prefix name -ide 9 = nona- 10 = deca- To write the name, write two words: One exception is we don’t write mono- if there is only one of the first element. No double vowels when writing names (oa oo) Prefix name Prefix name -ide

Name These N2O NO2 Cl2O7 CBr4 CO2 BaCl2

Write formulas for these diphosphorus pentoxide tetraiodine nonoxide sulfur hexafluoride nitrogen trioxide carbon tetrahydride phosphorus trifluoride aluminum chloride

Writing names and Formulas Acids Writing names and Formulas

Acids Compounds that give off hydrogen ions when dissolved in water. Must have H in them. will always be some H next to an anion. The anion determines the name.

Naming acids If the anion attached to hydrogen ends in -ide, put the prefix hydro- and change -ide to -ic acid HCl - hydrogen ion and chloride ion hydrochloric acid H2S hydrogen ion and sulfide ion hydrosulfuric acid

Naming Acids If the anion has oxygen in it, then it ends in -ate of -ite change the suffix -ate to -ic acid (use no prefix) HNO3 Hydrogen and nitrate ions Nitric acid change the suffix -ite to -ous acid HNO2 Hydrogen and nitrite ions Nitrous acid

Name these HF H3P H2SO4 H2SO3 HCN H2CrO4

Writing Acid Formulas Hydrogen will always be first name will tell you the anion make the charges cancel out. Starts with hydro?- no oxygen, -ide no hydro?, -ate comes from -ic, -ite comes from -ous

Write formulas for these hydroiodic acid acetic acid carbonic acid phosphorous acid hydrobromic acid

Section 6.6 Summary of Naming and Formula Writing OBJECTIVES: Use the flowchart in Figure 6.21 to write the name of a compound when given its chemical formula.

Section 6.6 Summary of Naming and Formula Writing OBJECTIVES: Use the flowchart in Figure 6.23 to write a chemical formula when given the name of a compound.

Helpful to remember... 1. In an ionic compound, the net ionic charge is zero (criss-cross method) 2. An -ide ending generally indicates a binary compound 3. An -ite or -ate ending means there is a polyatomic ion that has oxygen 4. Prefixes generally mean molecular; they show the number of each atom

Helpful to remember... 5. A Roman numeral after the name of a cation shows the ionic charge of the cation Use the handout sheets provided by your teacher!

Summary of Naming and Formula Writing For naming, follow the flowchart- Fig. 6.21, page 161 For writing formulas, follow the flowchart from Fig. 6.23, p. 162