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Chapter 5 Names and Formulas of Compounds. Homework  Assigned Problems (odd numbers only)  “Questions and Problems” 5.1 to 5.61 (begins on page 131)

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Presentation on theme: "Chapter 5 Names and Formulas of Compounds. Homework  Assigned Problems (odd numbers only)  “Questions and Problems” 5.1 to 5.61 (begins on page 131)"— Presentation transcript:

1 Chapter 5 Names and Formulas of Compounds

2 Homework  Assigned Problems (odd numbers only)  “Questions and Problems” 5.1 to 5.61 (begins on page 131)  “Additional Questions and Problems” 5.71 to 5.95 (page )  “Challenge Questions” 5.97 to 5.103, (page )

3 Octet Rule and Ions  Compounds are pure substances  The result of a combination of two or more elements held together by chemical bonds  Chemical bonds are the attractive forces that hold atoms or ions together  They can be ultimately broken down into two or more simpler substances: Elements

4 Octet Rule and Ions  Two types of attractive forces  Ionic: Involves the transfer of one (or more) electrons from one atom (or group) to another  For example, NaCl  Covalent: When two or more atoms share one or more electrons between them  For example, HF  In compounds with covalent bonds it is the outermost electrons involved in the chemical bonding

5 Octet Rule and Ions  When a compound forms, the atoms must lose, gain, or share electrons to produce a noble gas electron configuration  When the sodium atom loses its only valence electron, it obtains the electron configuration of its nearest noble gas: Neon The octet rule

6 Positive Ions  Form when an electron or electrons are lost from a metal  Named with element name, then add “ion”  Atom becomes charged  The charge on an ion is equal to the number of the electrons lost Sodium Magnesium Aluminum Calcium Sodium Ion Magnesium Ion Aluminum Ion Calcium Ion

7 Positive Ions  Ionic bonding involves transferring one or more electrons between two or more atoms  Produces a (+) charged atom: cation  Metals in groups IA, IIA, IIIA easily lose electrons to acquire the noble gas electron configuration

8 Negative Ions  Form when an electron or electrons are gained  Named with root of parent atom and adding -ide to the end  Atom becomes charged  The charge on an ion is equal to the number of the electrons gained Fluorine Bromine Oxygen Sulfur Fluoride Bromide Oxide Sulfide

9 Negative Ions  Ionic bonding and the transfer of electrons also produces a (-) charged atom: anion  Nonmetals in groups VA, VIA, VIIA will gain the necessary number of electrons to acquire the noble gas electronic configuration

10 Ionic Compounds  Compounds which are held together by the attraction of positive and negative ions: ionic compounds  Solid crystals formed by a very ordered packing of oppositely charged ions  Most ionic compounds are composed of a metal and a nonmetal  High melting temperatures

11 Ionic Compounds  Solids  They do not exist as single molecules  The formula represents the simplest ratio that these atoms combine together  Ions are packed together into a “lattice”  Held strongly together, high melting temperature

12 Charge Balance in Ionic Compounds  Binary ionic compounds are composed of only two elements (metal and nonmetal)  The symbol of the cation always precedes the symbol of the anion  The sum of the positive charges (cation) must equal the sum of the negative charges (anion)  Net charge is zero  Subscripts written as whole numbers indicate the number of each ion in the formula unit

13 Subscripts in Formulas  Sodium Chloride  Formed from sodium and chlorine atoms  An ionic bond forms consisting of a sodium ion (+ charge) and a chloride ion (- charge)  Each sodium loses one electron to achieve an octet  Each chlorine atom gains one electron to achieve an octet  Formula is NaCl

14 Subscripts in Formulas  Magnesium Chloride  Formed from magnesium and two chlorines  An ionic bond forms consisting of a magnesium ion (2+ charge) and two chloride ions (- charge each)  Each magnesium loses two electrons to achieve an octet  Each chlorine atom gains one electron to achieve an octet  Formula is MgCl 2

15 Writing Ionic Formulas from Ionic Charges  Subscripts in a formula represent the number of positive and negative ions  Write the formula for the ionic compound containing Na + and N 3- Na N Na + N 3- Net charge: 3(+1) + 1(3-)=0 Formula: Na 3 N Na Each loses 1e - Gains 3e -

16 Naming and Writing Ionic Formulas  Ionic Compounds Containing Two Elements  Compounds containing a metal and a nonmetal are binary ionic compounds  Single Cation Metals: Form one positive ion  Multiple Cation Metals: Form more than one positive ion  The systematic naming uses the name of the cation first, followed by the name of the anion  Subscripts in the formula are not included in the name

17 Types of Metal Ions  Single Cation Metals  Form only one type of ion (one possible charge)  Main group metals in groups IA, IIA, and some IIIA  i.e. Sodium only forms one ion (Na + ) in chemical reactions  Determine charge by position on the periodic table (also see table 5.3 on page 136)

18 Naming Ionic Compounds Containing Two Elements  Name metal cation first, name nonmetal anion second  Single metal cation name is the metal name only, drop the word “ion”  Nonmetal anion named by changing the ending on the nonmetal name to -ide Name of metal______name of nonmetal + -ide

19 Examples  NaI  Sodium Iodide  CaF 2  Calcium Fluoride  Li 2 O  Lithium Oxide  AgCl  Silver Chloride  KCl  Potassium Chloride  Na 3 P  Sodium Phosphide  Rb 2 S  Rubidium Sulfide  Mg 3 N 2  Magnesium Nitride

20 Types of Metal Ions  Multiple Cation Metals  Form two or more types of ions (variable possible charge)  Transition metals in groups 3B to 12B, and some 4A and 5A  For example, Iron forms two ions (Fe 2+ and Fe 3+ ) in chemical reactions  Determine charge by the “stock system” for naming ions  The metal name followed by a Roman numeral in parentheses to indicate its charge (see table 5.4 on page 137)

21 Multiple Cation Metal Compounds  Metal listed first in formula & name (same order as for Type I compounds)  Determine metal cation charge from anion charge  Use the metal name (cation) first followed by a Roman numeral in parentheses to indicate its charge  Common multiple cations in Table 5.4, page 137  Nonmetal anion named by changing the ending on the nonmetal name to -ide

22 Determining the Charge of the Cation from the Anion è Determine the charge of Cu in Cu 2 O è Write the name of the compound 1)Determine the charge of the cation from the anion  Cu 2 O - the nonmetal anion is O, since it is in Group 6A, its charge is -2  Since there are 2 Cu ions in the formula and the total positive charge is +2, divide by the number of cations so each Cu has a +1 charge

23 Naming Ionic Compound with Variable Charge Metal Ions 2)Name the cation by its element name and use a Roman numeral in parenthesis to indicate its charge  Copper (I) 3)Name the anion by changing the last part of its element name to –ide  Oxygen 4)Write the name of the cation first and the name of the anion second copper (I) oxide oxide

24 Examples  FeI 3  1(?)+3(-1)=0  Iron (III) Iodide  Cu 2 O  2(?)+1(-2)=0  Copper (I) Oxide  SnBr 2  1(?)+2(-1)=0  Tin (II) Bromide

25 Examples SnI 4 SnI 4 1(?)+4(-1)=01(?)+4(-1)=0 Tin (IV) iodideTin (IV) iodide HgO HgO 1(?)+1(-2)=01(?)+1(-2)=0 Mercury (II) OxideMercury (II) Oxide MnCl 2 MnCl 2 1(?)+2(-1)=01(?)+2(-1)=0 Manganese (II) ChlorideManganese (II) Chloride

26 Writing Formulas from the Name of an Ionic Compound  Usually involves a metal and a nonmetal 1)Identify the cation and the anion 2)Balance the charges to write the formula  If it is a multiple cation metal, the Roman numeral determines the charge of the cation 3)When writing the formula, take the name of the cation first, followed by the name of the anion

27 Writing Formulas from the Name of an Ionic Compound  Compound name is lithium chloride  Li + and Cl - are the ions  Balance the charges  Write the formula  LiCl is the formula using the subscripts from the charge balance 11

28 Writing Formulas from the Name of an Ionic Compound  Compound name is iron (III) oxide  Fe 3+ and O 2- are the ions  Balance the charges  Write the formula  Fe 2 O 3 is the formula using the subscripts from the charge balance 23

29 Polyatomic Ions  A group of atoms covalently bonded together into a single unit  The unit obtains a charge  Most PA ions are negatively charged  Oxyions (anions): P, S, C, or N covalently bound to one or more oxygens  Never occur independently, always associated with ions of opposite charge  Only one PA is positively charged  ammonium ion

30 Naming Polyatomic Ions  Must memorize name, formula and charge (Table 5.6 on page 142). Look for relationships between ions  Oxyions: The number of oxygen atoms bonded to the same element (i.e. P, S, or N) will determine the name of the ion  ~ate is most common  ~ite has one less oxygen bonded

31 Polyatomic Ions  ~ate, ~ite pairs of ions  The ion in the pair with the most oxygens is always the ~ate ion  The ion in the pair with one less oxygen is always the ~ite ion  Ion pair with a -3 charge  phosphate PO 4 3-, phosphite PO 3 3-  Ion pair with a -2 charge  sulfate (SO 4 2- ), sulfite (SO 3 2- )  Ion pair with a -1 charge  nitrate (NO 3 - ), nitrite (NO 2 - )

32 Polyatomic Ions  Group 7A elements can form more than two types of polyatomic ions (oxyions)  Additional prefixes are used to differentiate the ions  See page 142 (class text) and page 330 (lab text)  The number of oxygens attached to the central atom has an effect on the name of the ion  e.g. Polyatomic ions of chlorine, bromine and iodine

33 Polyatomic Ions  Example: Polyatomic ions of chlorine 1)-ate ion  chlorate = ClO 3 - 2)-chlorate ion with 1 more O than chlorate, use per- prefix  perchlorate = ClO 4 - 3)- chlorate ion with 1 less O, use -ite suffix  chlorite = ClO 2 - 4)-chlorite ion with 1 less O, use hypo- prefix  hypochlorite = ClO -

34 Writing Formulas for Compounds Containing Polyatomic Ions  Formulas are written like binary ionic compounds  Consider polyatomic ions as single units with a certain charge  Obtain the correct ratio of cation to anion to achieve a net charge of zero  Use parentheses if more than one of the same PA unit is needed in a formula  Use subscripts to indicate the number of a particular ion in a formula

35 Writing Formulas for Compounds Containing Polyatomic Ions  Compound name is magnesium carbonate  Mg 2+ and CO 3 2- are the ions  Balance the charges  Write the formula  MgCO 3 is the formula using the subscripts from the charge balance 11

36 Writing Formulas for Compounds Containing Polyatomic Acids  Compound name is calcium nitrate  Ca 2+ and NO 3 - are the ions  Balance the charges  Write the formula  Ca(NO 3 ) 2 is the formula using the subscripts from the charge balance 1 2

37 Naming Compounds Containing Polyatomic Ions  Named the same way as binary ionic compounds  Positive ion (metal) name is written first  Polyatomic ions name follows the metal  No prefixes are used in the name  Cation: Check to see if metal is single or multiple cation  Use the name of the PA ion given in table 5.6 on page 142

38 Writing Formulas for Compounds Containing Polyatomic Ions  Compound name is iron (III) sulfate  Fe 3+ and SO 4 2- are the ions  Balance the charges  Write the formula  Fe 2 (SO 4 ) 3 is the formula using the subscripts from the charge balance 2 3

39 Writing Formulas for Compounds Containing Polyatomic Ions  Compound name is ammonium phosphate  NH 4 + and PO 4 3- are the ions  Balance the charges  Write the formula  (NH 4 ) 3 PO 4 is the formula using the subscripts from the charge balance 31

40 Naming Compounds Containing Polyatomic Ions CaSO 4 CaSO 4 calcium sulfatecalcium sulfate Ca 2+ and SO 4 2-Ca 2+ and SO 4 2- Li 2 CO 3 Li 2 CO 3 lithium carbonatelithium carbonate Li +, CO 3 2-Li +, CO 3 2- Al(NO 3 ) 3 Al(NO 3 ) 3 aluminum nitratealuminum nitrate Al 3+, NO 3 -Al 3+, NO 3 -

41 Summary of Naming Ionic Compounds  Summary of guidelines when writing binary ionic compound  The symbol of the cation always precedes the anion  The sum of the positive charges must equal the sum of the negative charges: A net charge of zero  Whole numbers are written as subscripts to indicate the number of each ion in the formula

42 Covalent Compounds and Their Names  Involves a bond between two nonmetals  Bonds occur between similar or identical atoms  Nonmetals such as O, Br, or N do not tend to lose electrons (tend to gain them)  Electrons are shared and not transferred between atoms forming covalent bonds  Exist as individual molecule

43 Formation of a Hydrogen Molecule  The simplest covalent bonding condition  Hydrogen has one 1s electron  H atom requires one additional electron to obtain the stable noble gas configuration of helium  Each H atom contributes its one electron  The electron pair shared by the two atoms, forming diatomic hydrogen H 2

44 Formation of Octets in Covalent Molecules  Two identical nonmetal atoms  Each atom will share valence electrons with the other  The shared pair of electrons allow each atom to achieve a stable noble gas configuration  This configuration can be achieved by a single, double, or triple shared pair of electrons

45 Formation of Octets in Covalent Molecules  Two identical nonmetal atoms  H atom exists as a diatomic molecule by achieving a duet of electrons  F, Cl, Br, I, O, N exist as diatomic molecules by achieving an octet of electrons in their valence shells

46 Sharing Electrons Between Atoms of Different Elements  Two nonidentical nonmetal atoms  The number of covalent bonds an atom forms will equal the number of electrons needed to form a noble gas configuration  Each vacancy + unpaired electron combination in the valence shell can be used to form a two- electron bond  Each atom will share valence electrons with the other forming a shared pair of bonding electrons (achieves a stable noble gas configuration)

47 Names and Formulas of Covalent Compounds  Molecular binary compounds  Composed of two nonmetal elements  Naming a compound  Use the full (element ) name for the first nonmetal  Add the –ide ending to the full name of the second nonmetal  Second nonmetal named like the nonmetal in binary ionic compounds (anion)  Indicate the number of atoms by adding numerical prefixes

48 Names and Formulas of Covalent Compounds (table 5.11, page 151) Subscript Prefix used 1 mono~ (Usually omitted on the first atom) 2 di ~ 3 tri ~ 4 tetra ~ 5 penta ~ 6 hexa ~ 7 hepta ~ 8 octa ~ 9 nona ~ 10 deca ~

49 Names and Formulas of Covalent Compounds  In ionic compounds the subscripts are not mentioned in the name  Many compounds can exist for many pairs of nonmetallic elements (i.e. nitrogen and oxygen) BaCl 2 barium chloride barium dichloride Na 2 SO 4 sodium sulfate disodium sulfate nitrogen monoxidenitrogen dioxidedinitrogen monoxide

50 Molecular Binary (Covalent) Compounds  Naming binary molecular compounds from a formula  Name the first nonmetal by its element name  Name the second nonmetal by adding the –ide suffix  Add the prefixes to indicate the number of atoms  Whenever the vowels a and o or o and o appear together, the first vowel is dropped from the prefix for easier pronunciation Cl 2 O dichlorine monooxide P 4 O 6 tetraphosphorous hexaoxide dichlorine monoxide tetraphosphorous hexoxide

51 Examples  IF 5  iodine pentafluoride B2O3B2O3B2O3B2O3  diboron trioxide  NO 3  nitrogen trioxide

52 Examples AsCl 3 AsCl 3 arsenic trichloridearsenic trichloride CO 2 CO 2 carbon dioxidecarbon dioxide CO CO carbon monoxidecarbon monoxide

53 Molecular Binary (Covalent) Compounds  When writing a formula from the name of a binary molecular compound  You must know definition of the numerical prefixes used in naming covalent compounds (see table 5.11)  (you MUST memorize these prefixes) 1)Write the symbols in order the elements appear in the name 2)Identify the prefixes with the appropriate subscripts

54 Acids (Section 14.1)  Produce H + when dissolved in water  Composed of H + (cation) and an anion  Binary acids have H + cation and a nonmetal anion  Oxyacids have H + cation and a polyatomic anion (contain oxygen)

55 Naming Binary Acids  Use the prefix hydro- before the root name of the element  Add the suffix -ic and the word acid to the root name for the element  Example: HCl  hydrochloric acid  Example: HI  hydroiodic acid

56 Oxyacids  Produce H + and a polyatomic ion when dissolved in water  Composed of hydrogen, oxygen, and another nonmetal  Use the root name of the polyatomic ion  If it ends in -ate use the suffix -ic acid  If it ends in -ite use the suffix -ous acid  Example: H 2 SO 4 (from SO 4 2-,sulfate ion)  sulfuric acid  Example: H 2 SO 3 (from SO 3 2-,sulfite ion)  sulfurous acid


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