Fundamentals D: Compound Nomenclature

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Department
Chemistry
Course
CHEM 1A
Professor
Ramesh D Arasasingham
Semester
Fall

Description
Chemical Principles: The Quest for Insight by Atkins and Jones 5 Edition Study Guide by Gigi ^-^ Fundamentals D Compound Nomenclature  many compounds were given informal, common names before their compositions were known ◦ sugar, water, quartz, ect.  Systematic names reveal which elements are present and sometimes the arrangements of atoms  chemical nomenclature – the systematic naming of compounds Naming of Cations  monatomic cation: ◦ same name as the element that forms it, plus the word “ion” ▪ Na = sodium ion  when an element can form more than one cation: ◦ write oxidation number (charge of cation) as Roman numerals in parentheses after name of element + 2+ ▪ Cu = copper(I) ion, = copper(II) ion  most transition metals (d-block in periodic table) form more than one cation ◦ unless given other info, use oxidation numbers in the names of their compounds  Some still use older systems of nomenclature: ◦ some cations were denoted with endings -ous (lower charge) and -ic (higher charge) ▪ these endings often added to Latin versions of atom names  iron (II) ion = ferrous ion  iron (III) ion = ferric ion ◦ this system is not used in the Atkins/Loretta book but make sure you know it. ◦ Common Cations – names and formulas (next page): Names of Anions  monatomic anions: ◦ add ending -ide to the name of element plus the word “ion” - 2- ▪ S = sulfide ion, O ion = oxide ion ◦ usually no need to specify charge because most elements that form monatomic anions only form one kind of ion ◦ halides – ions formed by halogens - - - - ▪ fluoride (F ), chloride (Cl ), bromide (Br ), and iodide (I )  Polyatomic anions: ◦ oxoanions – ions that include oxygen ▪ if only one oxoanion of an element exists, add ending -ate. 2-  Co3 = carbonate ion ▪ if two oxoanions exist:  give the atom with smaller number of oxygen atoms ending -ite  give atom with larger number of oxygen atoms ending -ate ▪ Nitrogen forms NO-and NO - 2 3 ▪ NO = nitrite and NO = nitrate 2 3 ◦ some atoms (particularly halogens) form more than two kinds of oxoanions ▪ the oxoanion with the smallest number of oxygen atoms is given prefix hypo- and suffix -ite  hypochlorite ion = ClO ▪ oxoanion with most oxygen atoms is given prefix per- and suffix -ate -  perchlorate ion = 4lO  Naming Oxoacids and Oxoanions ◦ the names of oxoanions and their parent acids can be determined by noting the oxidation number of the central atom and then referring to the table below 2- ▪ Nitrogen in2N2O has an oxidation number of +1 because it belongs to Group 15/IV (hyponitrite ion)  hydrogen is present in some anions ◦ the names of these anions begin with “hydrogen” - ▪ HS = hydrogen sulfide ▪ HCO = hydrogen carbonate 3 ◦ sometimes the name is written as one word (hydrogencarbonate) ◦ in an older nomenclature system, an anion with hydrogen uses prefix bi- instead of “hydrogen” - ▪ bicarbonate ion = hydrogen carbonate = HCO3 ◦ if two hydrogen atoms are present in anion, it is a dihydrogen anion ▪ H 2O 4 dihydrogen phosphate  Prefixes for naming compounds ◦ 1 – mono ◦ 2 - di ◦ 3 – tri ◦ 4 – tetra ◦ 5 – penta ◦ 6 – hexa ◦ 7 – hepta ◦ 8 – octa ◦ 9 – nona ◦ 10 – deca ◦ 11 – undeca (or hendeca) ◦ 12 - dodeca Names of Ionic Compounds  an ionic compound is named with the cation name first ◦ followed by name of anion ◦ omit the word “ion” completely  If cation comes from element with only one charge state such as (K or Cl ), omit oxidation number ◦ KCl = potassium chloride + - ◦ NH 4O 3 ammonium nitrate contains NH 4 and NO 3ons 2+ - ◦ since Co has more than oxidation number, C2Cl (with Cand Cl ions) is named cobalt (II) chloride ▪ note that the number of chloride ions depends on the need for charge balance  some ionic compounds form crystals that contain a set proportion of water molecules plus the ions of the compound itself, called hydrates ◦ copper (II) sulfate usually exists a4 CuS2 • 5H O ▪ raised dot separates water molecules from rest of formula. ▪ “5” indicates how many water molecules are present ◦ give the name of the compound first, then add “hydrate” with proper Greek prefix to indicate number of water molecules ◦ CuSO 4 5H 2 = copper (II) sulfate pentahydrate  if we wish to indicate a hydrate has lost its water molecules, call it anhydrous ◦ CuSO 4ithout its proper hydration is anhydrous copper(II) sulfate How to Name Ionic Compounds 1. Identify the cation and anion. 2. Decide the oxidation number of the cation by finding what charge is required to cancel the negative charge of the anion 3. name the cation 4. If the cation can have more than one oxidation number (most transition metals, some metals in Groups 12 – 15/V), give its charge a Roman numeral 5. name the anion. If the anion is monatomic, change the ending to -ide 6. For an oxoanion: 1. for elements that form two oxoanions, give the ion with the larger number of oxygen atoms -ate and that with smaller number of O atoms -ite 2. for elements that form four oxoanions, add the prefix hypo- to the oxoanion with fewest O atoms. Add prefix per- to oxoanion with most oxygen atoms 7. for other polyatomic atoms, find name of ion in tables given. 8. If hydrogen is present, add “hydrogen” to name of anion 9. if two hydrogen atoms are present, add “dihydrogen” 10. If water molecules are present, the compound is a hydrate. Add hydrate with proper Greek prefix corresponding to number preceding H O. 2  Example: ◦ name Na₂CO₃•10H₂O + ▪ sodium Na is the cation – “sodium” ▪ carbonate ion CO 2-is the anion – “sodium carbo
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