Rules for Assigning B) Oxidation State Determination Oxidation State (O.S.)* Oxidation and Reduction 1. O.S. of an atom in pure element = 0 For an atom, electrons can be lost or gained during a 2. O.S. of monoatomic ion = charge chemical reaction. 3. O.S. of Oxygen (O) is -2 in most of its covalent and ionic compounds (-1 in peroxides). If electrons are lost: OXIDATION The state becomes more positive 4. O.S. of H is +1 when combined with a non-metal 5. O.S. of H is -1 when combined with a metal If electrons are gained: REDUCTION The state becomes more negative 6. O.S. of Fluorine (F) is -1 in compounds
7. The sum of O.S. is 0 in compounds Oxidation State (O.S.) or Oxidation Number (O.N.) Number of electrons lost or gained during a chemical 8. The sum of O.S. equals charge in ions change * A compilation from different textbooks
Elements with Fixed Oxidation States (O.S.)*
Instead of memorizing elements that show different O.S., remember those that have a fixed one: Group 1 (IA) elements: Always +1 Group 2 (IIA) elements: Always +2 Aluminum, Al, and Scandium, Sc: Always +3 Zinc, Zn, and Cadmium, Cd: Always +2 Silver, Ag: Always +1
* A compilation from different textbooks
OXIDATION STATE DETERMINATION EXERCISES Assign oxidation state (O.S.) to each element in the following compounds:
a) SO3 i) CrCl3 2- 2- b) SO3 j) CrO4 2- c) KMnO4 k) Cr2O7
d) MnO2 l) HClO4
e) HNO3 m) HClO3
f) S8 n) HClO2
g) CH2Cl2 o) HClO
h) SCl2 p) K2SO4
C) A Nomenclature Proposal MORE GENERAL OBSERVATIONS Problematic of Nomenclature Coverage in Textbooks • Flow charts of various complexities (relatively often!) Flow charts, rules, … and tables, tables, tables … (Memorization!) ü From 3-box flow charts to 14-box ones GENERAL OBSERVATIONS • Link with acid/base concepts (sometimes, but rarely!) • Appears in chapters 2 or 3 of textbooks (often!) ü So, it is to be covered “at once”; as a single topic. ü Explanations on “hydrogen -ate/ite” ions (sometimes!) • Appears in end-of-textbook appendices (sometimes!) • Naming of hydrated salts (sometimes!) ü Very brief coverage, condensed guidelines • The “-ide”, “-ate”, and “-ite” cases (how are they • Tables of common ions (always!) linked and how they differ?) ü Monoatomic and polyatomic ions ü (and to the “-ic” and “-ous” ones too!) v Separated or altogether! • The Stock system (not always mentioned!) ü Oxidation states (charges) of metals (in figures or tables)
Elements (Symbol/Name) to Know (I) Elements (Symbol/Name) to Know (II)
1. H Hydrogen 13. Al Aluminum 25. Mn Manganese (NOT Mg) 38. Sr Strontium 2. He Helium 14. Si Silicon 26. Fe Iron 47. Ag Silver 3. Li Lithium 15. P Phosphorus (from Latin Ferrum) (from Latin Argentum) 4. Be Beryllium (NOT Phosphorous) 27. Co Cobalt (NOT Copper) 50. Sn Tin 5. B Boron (NOT Potassium) 28. Ni Nickel (NOT N) (from Latin Stannum) 6. C Carbon (NOT Ca) 16. S Sulfur (or Sulphur) 29. Cu Copper (NOT Co) 53. I Iodine 7. N Nitrogen (NOT Ni) 17. Cl Chlorine (NOT clorine) (from Latin Cuprum) 56. Ba Barium 8. O Oxygen 18. Ar Argon (NOT Arsenic) 30. Zn Zinc 78. Pt Platinum 9. F Fluorine 19. K Potassium (NOT P) 31. Ga Gallium 79. Au Gold (from Latin Aurum) (NOT Flourine) (from Latin Kalium) 32. Ge Germanium 80. Hg Mercury 10. Ne Neon 20. Ca Calcium (NOT Carbon) 33. As Arsenic (NOT Ar) (from Latin Hydrargyrum) 11. Na Sodium 21. Sc Scandium 34. Se Selenium (NOT S) 82. Pb Lead (from Latin Natrium) 22. Ti Titanium 35. Br Bromine (from Latin Plumbum) 12. Mg Magnesium (NOT Mn) 23. V Vanadium 36. Kr Krypton 92. U Uranium 24. Cr Chromium
Types of Chemical Compounds Language of Chemistry: Part 2: Binary Acids and Compounds Acid-Base Models: 1. A metal + a non-metal (e.g. NaCl) Brønsted-Lowry: Leads to ionic compounds! Acids are H+ donors, + Bases are H acceptors (need at least 1 atom with a lone pair). 2. A non-metal + another non-metal (e.g. CO2) Leads to covalent (or molecular) compounds! HF(aq) ⇌ F-(aq) + H+(aq) Acid conj. base
+ - NH3(aq) + H2O(l) ⇌ NH4 (aq) + OH (aq) Base conj. acid
Binary Covalent Compounds List of Binary Acids and Acids Binary Acids, Related Ions, and Covalent Compounds Covalent Covalent Acid Acid Related Ion Compound Compound Formula Name Ion Name Formula Name Groups 16/17 elements combined with hydrogen give binary covalent compounds in the gas state (g). HF(aq) Hydrofluoric acid F- Fluoride HF(g) Hydrogen fluoride
HBr(aq) Hydrobromic acid Br- Bromide HBr(g) Hydrogen bromide Group 16/17 elements combined with hydrogen give binary acids when dissolved in water (aq). HI(aq) Hydroiodic acid I- Iodide HI(g) Hydrogen iodide
® François Gauvin 2005
Nomenclature Names of Binary Binary Compounds Ionic Compounds (BINARY: made of only two elements) 1. Name the metal first. If the metal can have more than one oxidation state, the latter is specified by a Roman numeral between Ionic or Covalent Compound? parentheses (Stock System). There is NO SPACE BETWEEN METAL NAME AND OPENING Compound contains a metal Compound contains PARENTHESIS.
or ammonium ion (NH +) only nonmetals 4 Example: Cu+ and Cu2+ (copper cations) Cu+ is copper(I) ion; NOT copper (I) Name as an Name as a Cu2+ is copper(II) ion; NOT copper (II) Ionic Compound Covalent compound
Names of Binary Example 1 Ionic Compounds Name the following binary compound:
2. Then name the non-metal (i.e. the anion) FeCl2 by changing the ending of the non-metal Fe (metal) with Cl (non-metal) name to -ide (-ide suffix). → Ionic compound
Fe is iron (no fixed O.S.); Cl is chlorine. Refer to parent binary acid for ion name. Name non-metal with –ide suffix: chloride. Oxidation state of metal: For example: Chloride is from Hydrochloric acid, HCl, so it is Cl– Hydrochloric acid, HCl(aq) leads to In this compound, O.S.(Fe) is +2 → iron(II) chloride (Cl-) ion So the name is Iron(II) chloride.
Naming Binary Example 2 Covalent Compounds Name the following binary compound: Compounds made of two PF5 non-metallic elements Both P and F are non-metals. the more “metallic” element is No hydrogen in compound listed first → Covalent compound
(to the left or below); Most “metallic” is Phosphorus, The other element is treated Fluorine is treated as an anion → fluoride. as an anion; Use prefixes to indicate the number of atoms.
Prefixes are used to specify So the name is Phosphorus pentafluoride. the number of atoms
Example 3 Example 4 Give the formula of the following binary compound: Give the formula of the following binary compound:
Calcium Oxide Diphosphorus pentasulfide
Calcium is a metal → Ionic compound Its symbol is Ca. Phosphorus is a non-metal. Its symbol is P. Its oxidation state is fixed at +2 (Group 2 element). Sulfide is the anion of sulfur, S; another non-metal. So its charge is 2+, Ca2+.
Oxide is the anion of oxygen, O; the non-metal. Both elements of this compound are non-metals. Its charge is 2-, O2- (so O.S. of oxide ion is -2). → Covalent compound
Combine the two ions in order to cancel the positive and negative Prefixes in the compound name literally tell us what the charges. formula is: In this case, the 2+ charge of Ca cancels the 2- charge of O. Therefore, the formula should contain 1 Ca with 1 O. Di- means 2 and penta- means 5.
So the formula is CaO. So the formula is P2S5.
Example 5 Language of Chemistry: Give the formula of the following binary compound: Part 3: Oxoacids (HaZbOc) and Polyatomic Ion Compounds Chromium(III) oxide Case of Sulfuric Acid (loss of first H+ ion): Chromium is a metal (symbol is Cr) → Ionic compound. Its oxidation state is NOT fixed, but its value is +3 as H SO (aq) → HSO -(aq) + H+(aq) stated by the Roman numeral in the name, Cr3+ cation. 2 4 4 Oxide is the anion of oxygen, O; the non-metal. Acid conj. base
2- Its charge is 2-, O (so O.S. of oxide ion is -2). - HSO4 ANION Combine the two ions in order to cancel the positive and negative + charges. Case of sulfuric Acid (loss of second H ion): In this case, 2 Cr3+ ions (total charge 6+) would cancel the charge of 3 O2- ions (total charge 6-). - 2- + HSO4 (aq) → SO4 (aq) + H (aq) Therefore, the formula should contain 2 Cr with 3 O. Acid conj. base
2- So the formula is Cr2O3. SO4 ANION
Language of Chemistry: Nomenclature of Nomenclature of Polyatomic Ion Compounds Polyatomic Ion Compounds 1. Name the metal (or ammonium ion) first. If the metal can have more than one Binary or Polyatomic ion Compound? oxidation state, the latter is specified by a Roman numerals between parentheses (Stock System). There is NO SPACE Compound contains only Compound contains MORE BETWEEN METAL NAME AND OPENING TWO elements than TWO elements (including O) PARENTHESIS.
Name as a Name as a Polyatomic 2. Name the anion from its parent oxoacid, Binary Compound Ion Compound using the –ate or –ite suffix depending on the name of the parent oxoacid (see next slide).
Polyatomic ions List of Oxoacids and Related from oxoacids Polyatomic Ions (I) General Rule: Acid Related Acid Name Ion Name ___ic acid leads to ___ate ion Formula Ion ___ous acid leads to ___ite ion - HNO3 Nitric acid NO3 Nitrate
HNO Nitrous acid NO - Nitrite + - 2 2 Examples: HNO3 → H + NO3 2- Nitric Nitrate SO4 Sulfate H SO Sulfuric acid 2 4 - acid ion HSO4 Hydrogen sulfate 2- SO3 Sulfite + - H SO Sulfurous acid HNO → H + NO 2 3 - 2 2 HSO3 Hydrogen sulfite Nitrous Nitrite ® François Gauvin 2005 acid ion
List of Oxoacids STRONG ACIDS1 and Related HCl Hydrochloric acid Polyatomic Ions (II) HBr Hydrobromic acid Acid Related Acid Name Ion Name Formula Ion HI Hydroiodic acid 3- PO4 Phosphate Phosphoric H PO HPO 2- Hydrogen phosphate HNO3 Nitric acid 3 4 acid 4 H PO - Dihydrogen phosphate 2 4 HClO4 Perchloric acid 3- PO3 Phosphite Phosphorous H SO Sulfuric acid H PO HPO 2- Hydrogen phosphite 2 4 3 3 acid 3 - 1 From Table 15.3 of N.J. Tro; Chemistry, A Molecular Approach; H2PO3 Dihydrogen phosphite Pearson Education, 2008, page 670 (and other sources). ® François Gauvin 2005
Example 6 Example 7 Name the following compound: Name the following compound:
MgHPO4 CuSO3 Mg with HPO4 Cu with SO3
Mg is Magnesium: Group 2 element; Cu is Copper: Transition metal element; Always (+2) O.S.: Mg2+ O.S. is not fixed. 2- 2- Therefore, anion is HPO4 ; Anion is SO3 because Parent acid is H3PO4 (phosphoric acid). parent acid is H2SO3 (sulfurous acid). So the anion name is hydrogen phosphate. So the anion name is sulfite. Compound name: Copper must be in a +2 O.S.: Cu2+, copper(II) Magnesium hydrogen phosphate Compound name: Copper(II) sulfite
Example 8 Example 9 Give the formula of the following compound: Give the formula of the following compound:
Calcium nitrite Iron(III) sulfate
Calcium is a metal of group 2; its symbol is Ca. Iron is a transition metal; its symbol is Fe. Its oxidation state is fixed at +2 (Group 2 element). Its oxidation state is not fixed, So its charge is 2+, Ca2+. but it is specified in the compound name: iron(III), Fe3+.
The parent acid of nitrite ion is nitrous acid (HNO ). The parent acid of sulfate ion is sulfuric acid (H2SO4). 2 2- Therefore, nitrite charge is 1-, NO -. Therefore, sulfate charge is 2-, SO4 . 2
Combine the two ions in order to cancel the positive and negative Combine the two ions in order to cancel the positive and negative charges. charges. In this case, 2 Fe3+ ions (total charge 6+) would cancel the charge of 3 In this case, the 2+ charge of Ca2+ cancels TWO 1- charge of NO -. 2- 2 SO4 ions (total charge 6-). Therefore, the formula should contain 1 Ca with 2 NO2. Therefore, the formula should contain 2 Fe with 3 SO4.
So the formula is Fe (SO ) So the formula is Ca(NO2)2 2 4 3
NOMENCLATURE EXERCISES (I) NOMENCLATURE EXERCISES (II) Name Formula Name Formula
SiCl4 Al2(SO3)3 Cobalt(II) sulfate Lithium sulfide
CuH2PO4 TiCl3 Calcium hypochlorite Iron(III) nitrate
Cl2O N2O5 Potassium perbromate Copper(II) phosphate
Ti2O3 P4S3 Nitrogen trifluoride Lead(II) carbonate