Molecules and compounds

Section Forming compounds Assignment= Problem set #1

 All pure substances have constant composition. All samples of a pure substance contain the same elements in the same percentages (ratios). Mixtures have variable composition. Tro's "Introductory Chemistry", Chapter 5 3

 The smallest piece of a compound is called a molecule.  Every molecule of a compound has the same number and type of atoms.  Since all molecules of a compound are identical, every sample of the compound will have the same properties. Tro's "Introductory Chemistry", Chapter 5 4

Water has a constant mass ratio of oxygen to hydrogen of Show how hematite has a constant composition if one sample has 7.2 g Fe and 2.8 g O and a second sample has 18.1 g Fe and 6.91 g O.

 They describe the number and type of each atom in the simplest unit of the compound. Molecules or ions.  Each element is represented by its letter symbol.  The number of atoms of each element is written to the right of the element as a subscript. If there is only one atom, the 1 subscript is not written.  Polyatomic groups are placed in parentheses. If more than one. 6

 Ions made of more then one element  Not a compound  Have a charge  Memorize them for your daily quizzes!

Chlorate Carbonate Phosphate Ammonium Acetate Iodate Nitrate Cyanide Bicarbonate Sulfate Hydroxide

 Metals are written first. NaCl  Nonmetals are written in order from Table 5.1. CO 2 There are occasional exceptions for historical or informational reasons.  H 2 O, but NaOH. Tro's "Introductory Chemistry", Chapter 5 9 Table 5.1 Order of Listing Nonmetals in Chemical Formulas CPNHSIBrClOF

Tro's "Introductory Chemistry", Chapter 5 10 Mg(NO 3 ) 2 Compound called magnesium nitrate. Symbol of the polyatomic ion called nitrate. Symbol of the polyatomic ion called sulfate. CaSO 4 Compound called calcium sulfate. Implied “1” subscript on magnesium. Implied “1” subscript on calcium. Parentheses to group two NO 3 s.No parentheses for one SO 4.

11

 Certain elements occur as diatomic molecules.  7 diatomic elements— 12 H2H2 Cl 2 Br 2 I2I2 7 7A N 2 O 2 F 2

IONICCOVALENT  Formed from two ions  Consists of a METAL and a nonmetal or polyatomic ion  Formed from two NONMETALS

 Two or more nonmetals.  Smallest unit is a molecule. Tro's "Introductory Chemistry", Chapter 5 14

 Metals + nonmetals.  No individual molecule units, instead have a 3- dimensional array of cations and anions made of formula units. Tro's "Introductory Chemistry", Chapter 5 15

 Aluminum, Al.  Aluminum chloride, AlCl 3.  Chlorine, Cl 2.  Acetone, C 3 H 6 O.  Carbon monoxide, CO.  Cobalt, Co. Tro's "Introductory Chemistry", Chapter 5 16 PRACTICE

 Ionic compounds are made of ions.  Ionic compounds always contain positive and negative ions Cations = + charged ions; anions = − charged ions.  Ionic compounds have no charge 17

1. Write the symbol for the metal cation and its charge. 2. Write the symbol for the nonmetal anion and its charge. 3. Switcheroo! Charge (without sign) becomes subscript for the other ion. 4. Reduce subscripts to smallest whole-number ratio. 5. Check that the sum of the charges of the cation cancels the sum of the anions. Tro's "Introductory Chemistry", Chapter 5 18

 Potassium ion with a nitride ion.  Calcium ion with a bromide ion.  Aluminum ion with a sulfide ion. Tro's "Introductory Chemistry", Chapter 5 19

Naming ionic and molecular compounds Assignment= Problem set #2

Tro's "Introductory Chemistry", Chapter 5 21  H 2 O = Water, steam, ice.  NH 3 = Ammonia.  CH 4 = Methane.  NaCl = Table salt.  C 12 H 22 O 11 = Table sugar.

Tro's "Introductory Chemistry", Chapter 5 22  Ionic compounds. Metal + nonmetal(s).  Metal first in formula. Binary ionic or compounds with polyatomic ions.  Molecular compounds. 2 or more nonmetals. Binary molecular (or binary covalent).  2 nonmetals. Acids—Formula starts with H.  Though acids are molecular, they behave as ionic when dissolved in water.  May be binary or oxyacid.

Tro's "Introductory Chemistry", Chapter 5 23  Made of cation and anion.  Name by simply naming the ions. If cation is:  Type I metal = Metal name.  Type II metal = Metal name (charge).  Polyatomic ion = Name of polyatomic ion. If anion is:  Nonmetal = Stem of nonmetal name + -ide.  Polyatomic ion = Name of polyatomic ion.

Tro's "Introductory Chemistry", Chapter 5 24  Contain metal cation + nonmetal anion.  Metal listed first in formula and name. 1. Name metal cation first, name nonmetal anion second. 2. Cation name is the metal name. 3. Nonmetal anion named by changing the ending on the nonmetal name to –ide.

Tro's "Introductory Chemistry", Chapter 5 25  Type I Metals whose ions can only have one possible charge.  1A, 2A, (Al, Zn, Ag). Determine charge by position on the periodic table.  1A = +, 2A = 2+, Al = 3+. Some need to be memorized.  Zn = 2+, Ag = +.  Type II Metals whose ions can have more than one possible charge. Determine charge by charge on anion. How do you know a metal cation is Type II?

Tro's "Introductory Chemistry", Chapter 5 26  Contain metal cation + nonmetal anion.  Metal listed first in formula and name. 1. Name metal cation first, name nonmetal anion second. 2. Metal cation name is the metal name followed by a roman numeral in parentheses to indicate its charge. Determine charge from anion charge. Common Type II cations in Table Nonmetal anion named by changing the ending on the nonmetal name to –ide.

Tro's "Introductory Chemistry", Chapter Copper(II) ion with a nitride ion. 2. Iron(III) ion with a bromide ion.

Tro's "Introductory Chemistry", Chapter 5 28  KCl  MgBr 2  Al 2 S 3

Metal and a polyatomic ion 1. Name the metal 2. Name the polyatomic ion ** DO NOT CHANGE THE ENDING!!!!

 KNO 3  Mg(OH) 2  NH 4 NO 3

Tro's "Introductory Chemistry", Chapter Aluminum ion with a sulfate ion. 2. Chromium(II) with hydrogencarbonate.

NameFormula AcetateC2H3O2–C2H3O2– CarbonateCO 3 2– Hydrogencarbonate (aka bicarbonate) HCO 3 – HydroxideOH – NitrateNO 3 – NitriteNO 2 – ChromateCrO 4 2– DichromateCr 2 O 7 2– AmmoniumNH 4 + NameFormula HypochloriteClO – ChloriteClO 2 – ChlorateClO 3 – PerchlorateClO 4 – SulfateSO 4 2– SulfiteSO 3 2– Hydrogen sulfate (aka bisulfate) HSO 4 – Hydrogen sulfite (aka bisulfite) HSO 3 –

Tro's "Introductory Chemistry", Chapter NH 4 Cl 2. Ca(C 2 H 3 O 2 ) 2 3. Cu(NO 3 ) 2

Tro's "Introductory Chemistry", Chapter 5 34  We will not learn the rules for molecular compounds with more than 2 elements.  For binary molecular: Name first nonmetal. Then name second nonmetal with -ide ending. Then give each name a prefix to indicate its subscript in the formula.

1. Name first element in formula first. Use the full name of the element. 2. Name the second element in the formula with an − ide, as if it were an anion. However, remember these compounds do not contain ions! 3. Use a prefix in front of each name to indicate the number of atoms. Never use the prefix mono- on the first element.

Tro's "Introductory Chemistry", Chapter 5 36  1 = mono- Not used on first nonmetal.  2 = di-  3 = tri-  4 = tetra-  5 = penta-  6 = hexa-  7 = hepta-  8 = octa-  Drop last “a” if name begins with vowel.

Tro's "Introductory Chemistry", Chapter 5 37  NO 2  PCl 5  I 2 F 7

Review problem set #1&2 5.9 naming acids Assignment= Problem set #3

 Bromate  Chromate  Dichromate  Permanganate  Thiosulfate

 Didn’t you say we had to memorize these?  Lets look at the polyatomic ions and how they differ!!!

NO -1 Hyponitrite NO2 -1 Nitrite NO3 -1 Nitrate NO4 -1 Pernitrate

Tro's "Introductory Chemistry", Chapter 5 42  Acids are molecular compounds that often behave like they are made of ions.  All names have acid at end.  Binary Acids = Hydro- prefix + stem of the name of the nonmetal + -ic suffix.  Oxyacids: If polyatomic ion ends in –ate = Name of polyatomic ion with –ic suffix. If polyatomic ion ends in –ite = Name of polyatomic ion with –ous suffix.

43  Acids are molecular compounds that form H + when dissolved in water  Sour taste  Dissolve many metals Like Zn, Fe, Mg, but not Au, Ag, Pt.  Formula generally starts with H E.g., HCl, H 2 SO 4.

44  Contain H +1 cation and anion In aqueous solution  Binary acids have H +1 and nonmetal  Oxyacids have H +1 and polyatomic

45  Write a hydro- prefix.  Follow with the nonmetal name.  Change ending on nonmetal name to –ic.  Write the word acid at the end of the name.

 HBr  HF  HI

Perbromic Acid HBrO4 Bromic Acid HBrO3 Bromous Acid HBrO2 Hypobromous Acid HBrO

48 1. H 2 S 2. HClO 3 3. HNO 2

49  When name ends in acid, formulas starts with H.  Hydro- prefix means it is binary acid, no prefix means it is an oxyacid.  For an oxyacid, if ending is –ic, polyatomic ion ends in –ate; if ending is –ous, polyatomic ion ends in –ous.

50 1. Chloric acid 2. Phosphoric acid 3. Hydrobromic acid

 Problem Set #3 Page 151  # 73, 74, 75, 76

5.10- Review of Nomenclature 5.11-Formula Mass Assignment= Study for Chapter 5 Quest on day six

Tro's "Introductory Chemistry", Chapter 5 53

 Potassium Chloride  Aluminum Oxide  Potassium Sulfide  Magnesium Hydroxide

 HNO 3  H 2 SO 4  H 2 SO 3

Tro's "Introductory Chemistry", Chapter 5 56  The mass of an individual molecule or formula unit.  Also known as molecular mass or molecular weight.  Sum of the masses of the atoms in a single molecule or formula unit. Whole = Sum of the parts. Mass of 1 molecule of H 2 O = 2(1.01 amu H) amu O = amu.

Tro's "Introductory Chemistry", Chapter 5 57