Chapter 9 Naming Simple Compounds

Chapter 9 Naming Simple Compounds

Monatomic Ions Ionic compounds consists of a positive metal ion and a negative nonmetal ion combined in a proportion such that their charges add up to a net charge of zero. NaCl consists of one Na + and one Cl. Monatomic ions Monatomic ions consists of a single atom with a positive or negative charge resulting from the loss or gain of one or more valence electrons. These are seen as elements on the Periodic Table which become ions.

Monatomic Ions Cations Cations tend to lose valence electrons. (1+ charge lose 1 electron, 2+ charge lose 2 electrons, etc. ) When the metals in Groups 1A, 2A, and 3A lose electrons, they form cations with positive charges equal to their group number. The name of the cations of the Group 1A, 2A and 3A are the same as the name of the metal, followed by the word ion or cation. Na + is sodium ion, Ca 2+ is calcium ion, Al 3+ is aluminum ion.

Monatomic Ions Anions Nonmetals tend to gain electrons for form anions, so the charge of a nonmetallic ion is negative. The charge of any ion of a Group A nonmetal is determined by subtracting 8 from the group number. Group 7A form anions with a 1 charge (78 = 1) Anion names start with the stem of the element name and end in ide. Anion of fluorine is fluoride ion (F ), anion of chlorine is chloride ion (Cl )

Ions of Transition Metals Many of the transition metals (Group 1B 10B) form more than one cation with different ionic charges. Two methods are used to name these ions. Stock System a Roman numeral in parentheses is placed after the name of the element to indicate the numerical value of the charge. Fe 2+ is iron(ii) ions Fe 3+ is iron(iii) ion. Classical name of the element is used to form the root name for the element. This system is useful only if there only two ions! (Remember: ic is higher than ous) Fe 2+ is ferrous ion Fe 3+ is ferric ions

Fe2+ iron(ii) / ferrous Ag1+ silver Fe3+ iron(iii) / ferric Cd2+ cadmium Hg1+ mercury(i) / mercurous Zn2+ Au1+ zinc gold(i) / aurous Hg2+ mercury(ii) / mercuric Au3+ gold(iii) / auric Mn2+ manganese(ii) Co2+ cobalt(ii) / cobaltous Mn3+ manganese(iii) Co3+ cobalt(iii) /cobaltic Mn4+ manganese(iv) Cr2+ chromium(ii) / chromous Ni2+ nickel(ii) / nickelous Ni3+ nickel(iii) / nickelic Cr3+ chromium(iii) /chromic Pb2+ lead(ii) /plumbous Cu1+ copper(i) / cuprous Pb4+ lead(iv) / plumbic Cu2+ copper(ii) /cupric

Polyatomic Ions Polyatomic Ions are charged particles composed of more than one atom tightly bound together. Sulfate ions (SO 4 2 ) is composed of one sulfur atom and four oxygen atoms. It is not a combination of one Sulfur ion and two Oxygen ions! Polyatomic ions are a tightly bound group of atoms that behave as a unit and carry a charge. The names of most polyatomic anions often end in ite or ate.

+1 CHARGE ion 1 CHARGE name ion name H 2 PO 3 dihydrogen phosphite NH 4 + ammonium H 2 PO 4 dihydrogen phosphate HCO 3 hydrogen carbonate HSO 3 hydrogen sulfite H 3 O + hydronium HSO 4 hydrogen sulfate NO 2 nitrite NO 3 nitrate Hg 2 2+ mercury(i) OH CH 3 COO hydroxide acetate

1 CHARGE 1 CHARGE ion name ion name CrO 2 chromite BrO hypobromite CN cyanide BrO 2 bromite CNO cyanate BrO 3 bromate CNS thiocyanate BrO 4 perbromate O 2 superoxide IO hypoiodite MnO 4 permanganate IO 2 iodite ClO hypochlorite IO 3 iodate ClO 2 chlorite IO 4 periodate ClO 3 chlorate AlO 2 aluminate ClO 4 perchlorate N 3 azide

2 CHARGE 2 CHARGE ion name ion name HPO 3 2 hydrogen phosphite C 2 2 carbide HPO 4 2 hydrogen phosphate C 2 O 4 2 CrO 4 2 oxalate chromate CO 3 2 carbonate Cr 2 O 7 2 dichromate 2 SO 3 2 SO 4 sulfite sulfate C 4 H 4 O 6 2 MoO 4 2 tartrate molybdate S 2 O 3 2 thiosulfate O 2 2 peroxide SiO 3 2 silicate S 2 2 disulfide

3 CHARGE 4 CHARGE ion name ion name PO 3 3 phosphite P 2 O 7 4 pyrophosphate PO 4 3 phosphate PO 2 3 hypophosphite AsO 3 3 arsenite AsO 4 3 arsenate

End of Section 9.1

Naming Binary Ionic Compounds A binary compound is composed of two elements (in any proportion) and can be either ionic or molecular (covalent) To name any binary ionic compound, place the cation name first, followed by the anion name. Cs 2 O is cesium oxide Cu 2 O is copper(i) oxide NaBr is sodium bromide CuO is copper(ii) oxide H 2 O is a covalent compound (Chpt 8) called water.

Writing Formulas Binary Ionic Compounds Write the symbol of the cation and then the anion. Add whatever subscripts are needed to balance the charges. The positive charge of the cation must balance the negative charge of the anion so that the net ionic charge of the formula is zero. K + + Cl KCl Ca 2+ + Br CaBr 2 Fe 3+ + O 2 Fe 2 O 3 Use the crisscross method crisscross method the numerical value of the charge of each ion is crossed over and becomes the subscript for the other ion. Bring subscripts to lowest whole ratio!

Writing Formulas Polyatomic Ionic Compounds An ate or ite ending on the name of a compound indicates that the compound contains a polyatomic anion that includes oxygen. Write the symbol for the cation followed by the formula for the polyatomic ion and balance the charges. Ca 2+ + NO 3 Ca(NO 3 ) 2 Sr 2+ + SO 3 2 SrSO 3 Li + + CO 3 2 Li 2 CO 3 Use the crisscross method the numerical value of the charge of each ion (polyatomic too) is crossed over and becomes the subscript for the other ion.

Naming Polyatomic Ionic Compounds First recognize that the compound contains a polyatomic ion. State the cation first and then the anion NaClO sodium hypochlorite (NH 4 ) 2 C 2 O 4 ammonium oxalate Li 2 CO 3 lithium carbonate

End of Section 9.2

Naming Molecular Compounds Binary ionic compounds are composed of the ions of two elements, a metal and a nonmetal. Binary molecular compounds are composed of two elements, two nonmetals and they are not ions. Binary molecular compounds are composed of atoms, not ions, so ionic charges cannot be used to write formulas or to name them. In addition, when two nonmetallic elements combine, the often do so in more than one way. (CO, CO 2 ) Prefixes in the names of binary molecular compounds help distinguish compounds containing different amounts of the same two elements.

Naming Molecular Compounds The prefix in the name of a binary molecular compound tells how many atoms of each element are present in each molecule of the compound. Prefix Number mono 1 di 2 tri 3 tetra 4 penta 5 hexa 6 hepta 7 octa 8 nona 9 deca 10

Naming Molecular Compounds The names of all binary molecular compounds end in ide. CO is carbon monoxide CO 2 is carbon dioxide If just one atom of the first element is in the formula, omit the prefix mono Name the elements in order listed in the formula Use prefixed to indicate the number of each kind of atom The suffix of the name of the second element is ide. N 2 O is dinitrogen monoxide SF 6 is sulfur hexafluoride.

Writing Formulas Molecular Compounds Use the prefixes in the name to tell you the subscript of each element in the formula. Then write the correct symbols for the two elements with the appropriate subscripts. Silicon Carbide SiC Dinitrogen tetroxide N 2 O 4 Diphosphorus trioxide P 2 O 3

End of Section 9.3 End of Chapter 7

Naming Acids Acid is a compound that contains one or more hydrogen atoms and produces hydrogen ions (H+) when dissolved in water. When naming acids, the acid consists of an anion combined with as many hydrogen ions s are needed to make the molecule electrically neutral. The general chemical formulas of acids is H n X. X is a monatomic or polyatomic anion n is a subscript indication the number of hydrogen ions combined with the anion.

Naming Acids Three rules are used to name acids. The name depends on the name of the anion and its suffix (ide, ite, ic) 1.a. When the name of the anion ends in ide, the acid name begins with the prefix hydro. b. The stem of the anion has the suffix ic and is followed by the word acid. H + + Cl HCl Hydrogen ion chloride ion hydrochloric acid H + + S 2 H 2 S Hydrogen ion sulfide ion hydrosulfuric acid

Naming Acids Three rules are used to name acids. The name depends on the name of the anion and its suffix (ide, ite, ic) 1.a. When the anion name ends in ite, the acid name is the stem of the anion with the suffix ous, followed by the word acid H + + SO 3 2 H 2 SO 3 Hydrogen ion sulfite ion sulfurous acid H + + IO 2 HIO 2 Hydrogen ion ioditeite ion iodousous acid

Naming Acids Three rules are used to name acids. The name depends on the name of the anion and its suffix (ide, ite, ic) 1.a. When the anion name end in ate, the acid name is the stem of the anion with the suffix ic followed by the word acid. H + + NO 3 HNO 3 Hydrogen ion nitrate ion nitricic acid H + + SO 4 2 H 2 SO 4 Hydrogen ion sulfate ion sulfuric acid

Writing Formulas for Acids Use the rules for writing the names of acids in reverse to write the formula for acids. Hydrobromic acid Hydro indicates the bromide ion HBr Phosphorousous acid ous indicates the phosphite ion H 3 PO 3 Formic acid ic and beginning with the anion name indicates the formate ate ion HCOOH

Bases A base is an ionic compound that produced hydroxide ions (OH )when dissolved in water. Bases are named the same way as other ionic compounds the name of the cation is followed by the name of the anion. NaOH is sodium hydroxide To write the formulas for bases, write the symbol for the cation followed by the formula for the hydroxide ion. (balance the ionic charges jusat as you do for any ionic compound) Aluminum hydroxide Al 3+ + OH Al(OH) 3 Ammonium hydroxide NH 4 + + OH NH 4 OH

End of Section 9.4 End of Chapter 7

Laws Governing Formulas & Names Law of Definite Proportions A chemical formula tells you (by subscripts) the ratio of atoms of each element in the compound. Ratios of atoms can also be expressed as ratios of masses. 100 g of MgS breaks down into 43.12g Mg and 56.88g of sulfur. 100g MgS 1 mol MgS 1 mol Mg 56.4g MgS 1 mol MgS 1 mol Mg 24.305g Mg = 43.12g Mg 100g MgS 1 mol MgS 1 mol S 32.06g S = 56.88g S 56.4g MgS 1 mol MgS 1 mol S

Laws Governing Formulas & Names The ratios of these masses is 43.12/56.88 = 0.758:1 The mass ratio of 0.758:1 does not change no matter how the magnesium sulfide is formed or the size of the sample. Law of Definite proportions states that in samples of any chemical compound, the masses of the elements are always in the same proportions. MgS illustrates the law of definite proportions

Laws Governing Formulas & Names The Law of Multiple Proportions Water (H 2 O) and hydrogen peroxide (H 2 O 2 ) are formed by the same two elements, they have different physical and chemical properties. Each compound obeys the law of definite proportions in every sample of hydrogen peroxide. (16g O : 1g H) In every sample of water, the mass ratio of O to H is always 8:1 (8g O: 1g H) If a sample of H 2 O 2 has the same mass of H as a sample of H 2 O, the ratio of the mass of O in the two compounds is exactly 2:1

Laws Governing Formulas & Names 16 g O (in H 2 O 2 has 1g H) = 16 = 2 = 2:1 8 g O (in H 2 O has 1 g H) 8 1 Law of multiple proportions states that whenever the same 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.

End of Chapter 9