Chapter 7 Notes Chemical Formulas & Chemical Compounds West Valley High School General Chemistry Mr. Mata

Standard 3d Determine the molar mass of a molecule from its chemical formula and atomic masses.Determine the molar mass of a molecule from its chemical formula and atomic masses.

Essential Question How do you write chemical formulas for chemical compounds using a set of standard rules?How do you write chemical formulas for chemical compounds using a set of standard rules?

IonsIons Ions: atom (groups of atoms = polyatomic ions) that have a charge.Ions: atom (groups of atoms = polyatomic ions) that have a charge. Number of protons (p + ) is not equal to the number of electrons (e - ).Number of protons (p + ) is not equal to the number of electrons (e - ). p + ≠ e - Cation: A positive ionCation: A positive ion Mg 2+, NH 4 1+Mg 2+, NH 4 1+ Anion: A negative ionAnion: A negative ion Cl , SO 4 Cl , SO 4  Ionic Bonding: Force of attraction between oppositely charged ions.Ionic Bonding: Force of attraction between oppositely charged ions.

Predicting Ionic Charges Group 1: Lose 1 e- to form +1 ions H +1 Li +1 Na +1 K +1

Predicting Ionic Charges Group 2: Loses 2 e-’s to form +2 ions Be +2 Mg +2 Ca +2 Sr +2 Ba +2

Predicting Ionic Charges Group 13: Loses 3 Loses 3 e-’s to form +3 ions B +3 Al +3 Ga +3

Predicting Ionic Charges Group 14: Lose 4 Lose 4 e-’s or gain 4 e-’s? Neither! Group 14 elements rarely form ions.

Predicting Ionic Charges Group 15: Gains 3 Gains 3 e-’s to form -3 ions N -3 P -3 As -3 Nitride Phosphide Arsenide

Predicting Ionic Charges Group 16: Gains 2 Gains 2 e-’s to form -2 ions O -2 S -2 Se -2 Oxide Sulfide Selenide

Predicting Ionic Charges Group 17: Gains 1 Gains 1 e- to form -1 ions F -1 Cl -1 Br -1 Fluoride Chloride Bromide I -1 Iodide

Predicting Ionic Charges Group 18: Stable Noble gases do not form ions! Stable Noble gases do not form ions!

Predicting Ionic Charges Groups : Many transition elements Many transition elements have more than one possible ionic charge. have more than one possible ionic charge. Iron(II) = Fe +2 Iron(III) = Fe +3

Predicting Ionic Charges Groups : Some transition elements Some transition elements have only one possible ionic charge. have only one possible ionic charge. Zinc (II) = Zn +2 Silver (I) = Ag +1

Writing Ionic Compound Formulas Example: Magnesium carbonate 1. Write the formulas for the cation and anion, including CHARGES! Mg +2 CO Check to see if charges are balanced. They are balanced! MgCO 3

Writing Ionic Compound Formulas Example: Iron(III) chloride 1. Write the formulas for the cation and anion, including CHARGES! Fe +3 Cl Check to see if charges are balanced. 3. Balance charges, if necessary, using subscripts. Not balanced! 3 FeCl 3

Writing Ionic Compound Formulas Example: Barium nitrate 1. Write the formulas for the cation and anion, including CHARGES! Ba +2 NO Check to see if charges are balanced. 3. Balance charges, if necessary, using subscripts. Use parentheses if you need more than one of a polyatomic ion. Not balanced! ( ) 2 Ba(NO 3 ) 2

Writing Ionic Compound Formulas Example: Ammonium sulfate 1. Write the formulas for the cation and anion, including CHARGES! NH 4 + SO Check to see if charges are balanced. 3. Balance charges, if necessary, using subscripts. Use parentheses if you need more than one of a polyatomic ion. Not balanced! ( ) 2 (NH 4 ) 2 SO 4

Writing Ionic Compound Formulas Example: Aluminum sulfide 1. Write the formulas for the cation and anion, including CHARGES! Al +3 S Check to see if charges are balanced. 3. Balance charges, if necessary, using subscripts. Not balanced! 23 Al 2 S 3

Writing Ionic Compound Formulas Example: Zinc hydroxide 1. Write the formulas for the cation and anion, including CHARGES! Zn +2 OH - 2. Check to see if charges are balanced. 3. Balance charges, if necessary, using subscripts. Use parentheses if you need more than one of a polyatomic ion. Not balanced! ( ) 2 Zn(OH) 2

Writing Ionic Compound Formulas Example: Aluminum phosphate 1. Write the formulas for the cation and anion, including CHARGES! Al 3+ PO Check to see if charges are balanced. They ARE balanced! AlPO 4

TOP SECRET!!! DO NOT REVEAL THIS SECRET TECHNIQUE TO ANY OTHER CHEMISTRY CLASS!!!DO NOT REVEAL THIS SECRET TECHNIQUE TO ANY OTHER CHEMISTRY CLASS!!!

Criss-Cross Shortcut Method Ex: Na +1 S 2- Na 2 S 1 = Na 2 S Na 2 S 1 = Na 2 S sodium sulfide sodium sulfide Ex: Mg 2+ Br -1 Mg 1 Br 2 = MgBr 2 Mg 1 Br 2 = MgBr 2 magnesium bromide magnesium bromide

Criss-Cross Shortcut Method Example: Al 3+ S 2- Al 2 S 3 = Al 2 S 3 = Al 2 S 3 aluminum sulfide Example: Al 3+ CO 3 2- Al 2 (CO 3 ) 3 = Al 2 (CO 3 ) 3 = Al 2 (CO 3 ) 3 aluminum carbonate

Naming Ionic Compounds 1. Cation first, then anion1. Cation first, then anion 2. Monatomic cation = name of element2. Monatomic cation = name of element Ca 2+ = calcium ionCa 2+ = calcium ion 3. Monatomic anion = root + -ide3. Monatomic anion = root + -ide Cl  = chlorideCl  = chloride CaCl 2 = calcium chlorideCaCl 2 = calcium chloride

Naming Ionic Compounds (continued) - some metals form more than one cation.- some metals form more than one cation. -use Roman numeral in name.-use Roman numeral in name. PbCl 2PbCl 2 Pb 2+ is cationPb 2+ is cation PbCl 2 = lead(II) chloridePbCl 2 = lead(II) chloride Metals with multiple oxidation states

Naming Binary Compounds - Compounds between two nonmetals.- Compounds between two nonmetals. -First element in formula is named first.-First element in formula is named first. -Second element named as if it were an anion.-Second element named as if it were an anion. -Use prefixes.-Use prefixes. -Only use mono on second element --Only use mono on second element - P 2 O 5 = CO 2 = CO = N 2 O = diphosphorus pentoxide carbon dioxide carbon monoxide dinitrogen monoxide

Calculating Formula Mass Calculate the formula mass of magnesium carbonate, MgCO g g + 3(16.00 g) = g

Calculating Percentage Composition Calculate the percentage composition of magnesium carbonate, MgCO 3. From previous slide: g g + 3(16.00 g) = g 100 %

Empirical formula: lowest whole number ratio of atoms in a compound. Molecular formula: true number of atoms of each element in the formula of a compound. Molecular: H2OH2O C 6 H 12 O 6 C 12 H 22 O 11 Empirical: H2OH2O CH 2 O C 12 H 22 O 11

Formulas for ionic compounds are ALWAYS empirical (lowest whole number ratio). Examples: NaClMgCl 2 Al 2 (SO 4 ) 3 K 2 CO 3

Empirical Formula Determination 1.Base calculation on 100 grams of compound. 2.Determine moles of each element in 100 grams of compound. 3.Divide each value of moles by the smallest of the values. 4.Multiply each number by an integer to obtain all whole numbers.

Empirical Formula Determination Adipic acid contains 49.32% C, 43.84% O, and 6.85% H by mass. What is the empirical formula of adipic acid?

Empirical Formula Determination (part 2) Divide each value of moles by the smallest of the values. Carbon: Hydrogen: Oxygen:

Empirical Formula Determination (part 3) Multiply each number by an integer to obtain all whole numbers. Carbon: 1.50 Hydrogen: 2.50 Oxygen: 1.00 x Empirical formula: C3H5O2C3H5O2

Chapter 7 SUTW Prompt Describe the differences between writing chemical formulas for molecular compounds and ionic compounds.Describe the differences between writing chemical formulas for molecular compounds and ionic compounds. Complete an 8-10 sentence paragraph using the SUTW paragraph format. Hilight using green, yellow, and pink.Complete an 8-10 sentence paragraph using the SUTW paragraph format. Hilight using green, yellow, and pink. Due Date: Tomorrow (start of class).Due Date: Tomorrow (start of class).