Naming Compounds. Ionic and Molecular Nomenclature

Transcription

1 Naming Compounds Ionic and Molecular Nomenclature

2 Lewis dot diagrams Lewis diagrams show only valence electrons Write the symbol (represents the nucleus and inner electrons) determine the number of outer electrons use a dot to indicate each valence electron

3 Negative Ions double up the electrons when all the positions have 1 electron already, each position can only hold 2 electrons

4 A binary ionic compound is formed between one metal ion and one non-metal ion. The metal donates valence electrons to become a positive ion. The non-metal accepts these electrons into its outer energy level to become a negative ion. For example: The positively charged sodium ion is attracted to the negatively charged chloride ion. This attraction is called an ionic bond.

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9 Magnesium has two valence electrons and oxygen has six. Magnesium has donated two electrons to one oxide ion. Calcium has two valence electrons and chlorine has seven. Calcium has donated two electrons to two chloride ions (they accept one each).

10 Ionic compounds do not form individual molecules, but exist as a crystal lattice structure. This is a regular three-dimensional pattern of alternating positive and negative ions producing an electrically neutral compound. This is very stable arrangement, so all ionic compounds are solid at room temperature. For sodium chloride, there is one sodium ion for every chloride ion (they are in a 1:1 ratio).

11 The chemical formula of an ionic compound represents the lowest whole number ratio of the ions in the crystal and it is called a formula unit. 1) Write the name of the metal (positive) ion first. 2) Write the name of the non-metal (negative) ion last and change the ending to -ide. examples: KBr(s) MgCl 2 (s) Na 2 S(s) potassium bromide magnesium chloride sodium sulfide The name of an ionic compound does not use prefixes to show the number of ions present.

12 Naming Compounds To prevent confusion, the International Union of Pure and Applied Chemists (IUPAC) has rules! Members of the IUPAC commission appointed to study chemical notation systems. 1951

13 Chemical Formulas (Ionic) All ionic compounds have a net charge of zero. e.g. Barium Fluoride Ba F - F - 1- x2 2- Net Charge 1+ 0 The formula is: BaF 2 (s)

14 Writing a Formula Write the formula for the ionic compound that will form between Ba 2+ and Cl. Solution: 1. Balance charge with + and ions 2. Write the positive ion of metal first, and the negative ion Ba 2+ Cl Cl 3. Write the number of ions needed as subscripts BaCl 2

15 When writing formulas of binary ionic compounds, the symbols for the elements are written in the same order as they appear in the name. Subscript numbers are used to indicate the ratio of the ions in the compound. The charges on the ions must balance in the chemical formula, since ionic compounds are electrically neutral. 1) Identify the ions and their charges. 2) Determine the ratio of charges needed to balance. 3) The charge on the metal ion crosses to become the subscript on the non-metal ion. Do not include the ( + ) sign. 4) The charge on the non-metal ion crosses to become the subscript on the metal ion. Do not include the ( ) sign. 5) Reduce the ratio of subscripts in the formula.

16 1) aluminum fluoride 3+ Al F AlF (s) 3 2) silver sulfide 3) potassium iodide Ag + S 2 Ag S(s) 2 + K I KI(s) 4) zinc nitride Zn 2+ N 3 Zn N (s) 3 2

17 Practice A. Sodium sulfide Na +, S 2- Na 2 S B. Aluminium chloride Al 3+, Cl - AlCl 3 C. Magnesium nitride Mg 2+, N 3- Mg 3 N 2

18 Learning Check Complete the names or formula of the following binary compounds: Na 3 N sodium KBr Al 2 O 3 MgS potassium aluminum magnesium Strontium oxide Sr 2 O 2 SrO

19 Multi-valent ions Transition metals and the metals in groups 14 and 15 can form more than 1 ion Fe, Cu, Sn The most common ion charge is written first on the periodic table The ion charge must form part of the name

20 Example Copper chloride : copper can form two ions, Cu 2+, Cu + Both ions can form compounds with chloride The two compounds have different properties

21 Multi - Valent Ions (p ) When the metal in an ionic compound is multivalent there are 2 methods: Classical (Latin) or Stock (IUPAC) Latin is older (not useful for some compounds) As before, the name ends in -ide & + is first The metal is named with its Latin or English root and ends in -ic or ous to denote valence E.g. Cu 1+ is cuprous, E.g. Cu 2+ is cupric Lower = ous, Higher = ic Be able to recognize these but you are not responsible to work with them.

22 Classical System Element (valence) English name Latin Name Higher valence Lower valence Metals that have and use latin names Cu (1,2) Copper Cuprum Cupric Cuprous Fe (2,3) Iron Ferrum Ferric Ferrous Pb (2,4) Lead Plumbum Plumbic Plumbous Sn (2,4) Tin Stannum Stannic Stannous Metals that do not have latin names Co (2,3) Cobalt - Cobaltic Cobaltous Cr (2,3) Chromium - Chromic Chromous Mn (2,3) Manganese - Manganic Manganous Metals that have latin names but use english root Hg (1,2) Mercury Hydrargyrum Mercuric Mercurous

23 Determining the Charge on a Multivalent Cation Au 2 S 3 1. determine the charge on the anion Au 2 S 3 - the anion is S, since it is in Group 16, its charge is determine the total negative charge since there are 3 S in the formula, the total negative charge is determine the total positive charge since the total negative charge is -6, the total positive charge is divide by the number of cations since there are 2 Au in the formula & the total positive charge is +6, each Au has a +3 charge

24 Names of Variable Ions Use a Roman number after the name of a metal that forms two or more ions FeCl 3 (Fe 3+ ) iron (III) chloride CuCl (Cu + ) copper (I) chloride SnF 4 (Sn 4+ ) tin (IV) fluoride PbCl 2 (Pb 2+ ) lead (II) chloride Fe 2 S 3 (Fe 3+ ) iron (III) sulfide

25 Learning Check Complete the names of the following binary compounds with variable metal ions: FeBr 2 Cu 2 O SnCl 4 Fe 2 O 3 CuS iron ( ) bromide copper ( ) oxide ( )

26 Solution Complete the names of the following binary compounds with variable metal ions: FeBr 2 Cu 2 O SnCl 4 Fe 2 O 3 CuS iron ( II ) bromide copper ( I ) oxide tin (IV) chloride iron (III) oxide copper (II) sulfide

27 Name the following Practice A. CaO calcium oxide B. PdCl 2 palladium(ii) chloride C. Co 2 O 3 cobalt (III) oxide

28 Ionic compounds with multivalent elements must have Roman numerals after the name of the positive (metal) ion to indicate the charge on that ion. Compound Name Formula iron(iii) chloride PbO 2(s) nickel(iii) sulfide copper(ii) fluoride chromium(iii) sulfide Use Roman numerals ONLY when the metal element is multivalent.

29 Ionic compounds with multivalent elements must have Roman numerals after the name of the positive (metal) ion to indicate the charge on that ion. Compound Name iron(iii) chloride lead(iv) oxide nickel(iii) sulfide copper(ii) fluoride chromium(iii) sulfide Formula FeCl 3(s) PbO 2(s) Ni2S 3(s) CuF 2(s) Cr2S 3(s)

30 Bonus Fe 3 O 4 is a mineral and one of the main iron ores. Name? Charges on the iron ions? iron(ii,iii) oxide

31 Polyatomic ions consist of a group of atoms combined together that exist as a single unit with an overall electric charge. Most polyatomic ions have a negative charge, which means they behave as non-metals. This means that they are always written last in the formula. The one exception: ammonium ion + NH 4 When writing the formula for compounds containing more than one of a polyatomic ion, the symbol for the ion must be written in brackets. Beauty eh.

32 Naming Ionic with Polyatomic Ion 1. Identify the ions Na 2 SO 4 2. Name the cation (positive ion) 3. Name the anion (negative ion) 4. Write the name of the cation followed by the name of the anion

33 Some Common Polyatomic Ions Name Formula acetate C 2 H 3 O 2 carbonate CO 3 2 hydrogen carbonate HCO 3 hydroxide OH nitrate NO 3 nitrite NO 2 chromate CrO 4 2 dichromate Cr 2 O 7 2 ammonium NH 4 + Name hypochlorite ClO Formula chlorite ClO 2 chlorate ClO 3 perchlorate ClO 4 sulfate SO 4 2 sulfite SO 3 2 Hydrogen sulfate (aka bisulfate) Hydrogen sulfite (aka bisulfite) HSO 4 HSO 3

34 Compound Name barium hydroxide iron (III) carbonate copper (I) permanganate gold (III) nitrate ammonium phosphate potassium dichromate Formula Ba OH 2 NH 3 3 PO (s) K Cr O (s) (s) Fe 2 CO 3 (s) 3 CuMnO 4(s) Au NO (s)

35 Patterns for Polyatomic Ions 1. elements in the same column form similar polyatomic ions same number of O s and same charge ClO 3- = chlorate \ BrO 3- = bromate 2. if the polyatomic ion starts with H, the name adds hydrogen- prefix before name and add 1 to the charge CO 3 2- = carbonate \ HCO 3 1- = hydrogen carbonate

36 Patterns for Polyatomic Ions -ate ion chlorate = ClO ate ion + 1 O same charge, per- prefix perchlorate = ClO ate ion 1 O same charge, -ite suffix chlorite = ClO ate ion 2 O same charge, hypo- prefix, -ite suffix hypochlorite = ClO 1-

37 Common Mistakes Be careful: sulfide = S 2- sulfate = SO 4 2- sulfite = SO 3 2- sulfur tetraoxide = SO 4 sulfur trioxide = SO 3 nitride = N 3- nitrate = NO 2-3 nitrite = NO - 2 nitrogen dioxide = NO 2 nitrogen trioxide = NO 3 ammonia = NH 3 ammonium = NH + 4

38 Hydrated ionic compounds are those ionic compounds which contain water molecules inside their crystal lattice The water is not chemically bonded to the crystal and may be driven off by heating the hydrated compound. Eg.) Copper(II) sulfate pentahydrate To write the chemical formula; write the ionic compound then write a "dot" followed by "H 2 O" the number corresponding to the prefix attached to the "hydrate" from the "word" equation.

39 ZnCl 2 6H 2 O is Zinc chloride hexahydrate Ba(OH) 2 8H 2 O is Barium hydroxide octahydrate

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41 Remember, for ionic compounds, a formula unit is a ratio of the number of ions in a crystal lattice. Ionic compounds do not form independent units. ionic compound A molecule is two or more non-metal atoms bonded together. Each molecule is independent of the next, and is not part of a lattice. molecular compound

42 Binary molecular compounds are formed between two non-metal elements. No metals??? No WAY!! Yeah, dude. Metal rules.

43 Remember that non-metals need to gain electrons to have a full outer shell. When non-metal atoms combine, the only way this can be achieved is if they share their outer electrons. a pair of shared electrons two chlorine atoms one chlorine molecule Cl (g) 2 Since electrons are being shared (always in pairs), there is a strong force of attraction between the two atoms. This force is a covalent bond.

44 two pairs of shared electrons an oxygen atom and two hydrogen atoms a water molecule

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46 The vast majority of elements exist in nature as single atoms. These are called monoatomic. There are a few diatomic elements (exist as pairs of atoms), which you must memorize. I 2 (g) Br 2 (g) Cl 2 (g) F 2 (g) O 2 (g) N 2 (g) H 2 (g) There are three polyatomic elements which also must be memorized. P 4 (s) S 8 (s) O 3 (ozone)

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48 The prefix mono- is not used when the first element is only one atom. This does not apply to the second element.

49 Name carbon dioxide dinitrogen monoxide phosphorus trichloride oxygen difluoride dinitrogen tetrasulfide sulfur trioxide Formula CO 2(g) N2O(g) PCl (g) 2 3 OF (g) N2S 4(g) SO (g) 3

50 read pages Worksheets: Page 37, 39 in workbook

51 Molecular Compounds That Contain Hydrogen Many have common names that you must memorize! IUPAC Name Water Hydrogen peroxide Ammonia Formula and state at 25 C H 2 O (l) H 2 O 2(l) NH 3(g) Sucrose C 6 H 12 O 11 Methane CH 4(g) Propane methanol Ethanol Hydrogen sulfide C 3 H 8(g) CH 3 OH (l) C 2 H 5 OH (l) H 2 S (g)

52 Molecular Compounds Form between nonmetals Electrons are shared (covalent bond) Solutions do not conduct electricity

53 Properties of Ionic Compounds High melting point (all of them are solids at room temp.) Retention of crystal shape Solubility (some are; some aren t) Conductivity ionic solutions are conductive; molecular solutions are not Ionic compounds that dissolve in water and conduct electricity as solutions are called electrolytes Electrolyte movie:

54 Solubility of Ionic Compounds Solubility is a measure of a compound s ability to dissolve in a solvent What s being dissolved is called the solute (e.g. Kool-aid mix) What s doing the dissolving is called the solvent (e.g. water)

55 An ionic compound dissolved in water is said to be aqueous. (Not liquid) eg. NaCl(s) = solid salt NaCl (l) = molten salt NaCl (aq) = salt dissolved in water

56 To see if ionic compounds will be soluble or insoluble in water, use the solubility table on the periodic table. Hint: Use the negative ion as a starting place is easiest.

57 Sodium phosphate

58 Solubility practice: NaOH CaSO 4 Mg(NO 3 ) 2 NH 4 Br AgCH 3 COO KI BaSO 4 MgS soluble (aq) insoluble (s) soluble (aq) soluble (aq) insoluble (s) soluble (aq) insoluble (s)?

59 Acids and Bases A. Properties 1. Acids a. Taste sour b. ph less than 7 c. Litmus turns red d. Bromothymol blue turns yellow

60 Bases a. Taste bitter b. Feel slippery c. Litmus turn blue d. Turns phenolphthalein pink e. ph > 7

61 The ph of a solution describes the amount of hydrogen ions in a solution (power of Hydrogen). a. ph ranges from 0 to 14 Pure water has a ph of 7 Below 7 is acidic Above 7 is basic

62 Acids Aqueous solutions Contain hydrogen, usually appears on the LEFT side of the formula HCl (aq) HNO 2 (aq) Acids are conductive, react with Mg and Ca to form hydrogen gas

63 Acids with carbon CH 3 COOH (aq) ethanoic acid or acetic acid CH 3 COOH the last hydrogen is the one that makes this an acid Look for the COOH portion of the formula

64 Naming acids IUPAC rules H 2 SO 4 (aq): aqueous hydrogen sulfate

65 Old Rules Hydrogen with a non-metallic element HCl Hydrogen chloride becomes hydrochloric acid when in solution HF (aq) is hydrofluoric acid

66 Old Rules H 2 SO 4 (aq) aqueous hydrogen sulfate becomes Sulfuric acid H 3 BO 3 (aq) aqueous hydrogen borate boric acid

67 Bases Ionic compounds usually containing hydroxide ion (OH - ) NaOH (aq) Compounds with NH 4+ also are bases Bases are conductive

68 HNO 3(aq) acid NaOH (aq) Acid, Base or Neutral? Base: ionic compound with hydroxide ion CH 3 OH (aq) Neutral: molecular compound (all nonmetal atoms) NH 4 OH(aq) Base: ionic compound with hydroxide ion