Naming And Writing Compounds PDF

GEN 0103 NAMING AND WRITING COMPOUNDS Engr. Veronica F. Acosta GE Faculty College of Engineerin...

GEN 0103 NAMING AND WRITING COMPOUNDS Engr. Veronica F. Acosta GE Faculty College of Engineering University of Perpetual Help System DALTA 1. Learning Outcomes At the end of this module, the student should be able to a. Differentiate molecular compound from ionic compound. b. Write the correct formulas for different substances. c. Give the correct name of different substances. 2. Introduction This module gives the notion of ionic compounds and molecular compound. It focuses on the rules in naming and writing compounds. This is a narrow topic and provides only condensed information. Hence, the reader is advised to treat it as a guide for a more detailed readings. 3. Formula – a combination of symbols that identifies a compound, an ion or a molecule of an element. -also indicates the relative quantities of the elements contained in the compound or ion and implies some kind of chemical bonding between the atoms. A molecule contains two or more nonmetallic atoms bonded together. Seven elements occur as diatomic molecules (molecules with two atoms) when they are not combined with other elements. H2 , N2 , F2 , O2 , I2 , Cl2 , Br2 Formula Units The collection of atoms represented by a formula is called a formula units. A chemical formula consists of symbols of element(s) often with subscripts that tells how many atoms of each element are present per formula unit. Parentheses may be used in a formula to group bonded atoms together, and a subscript after the closing parenthesis tells how many of that group are present per formula unit. Examples: CO One carbon atom and one oxygen atom are bonded in one formula unit Br2 Two atoms of bromine are bonded in one formula unit H2O Two atoms of hydrogen and one atom of oxygen are bonded in one formula unit (NH4)PO4 Three NH4 groups, each containing one atom of nitrogen and four hydrogen atoms and one phosphorus atom and four oxygen atoms are present in one formula unit. Ionic compounds are always neutral; no net charge is present. The total positive charge present on the ions that have lost electron always is exactly counterbalanced by the total negative charge on the ions that have gained electrons. RULES IN WRITING CHEMICAL FORMULAS 1. Write the symbol of the positive ion (can be either a monoatomic or polyatomic ion) first then the negative ion (can be either a monoatomic or polyatomic ion). Monoatomic ion – composed of one kind of atom only Polyatomic ion - composed of two or more different kinds of atom 2. Balance the charges of the monoatomic ion or polyatomic ions by writing subscript after each symbol to give an algebraic sum of zero. The subscripts indicates the number of atoms or polyatomic ions needed in the formula. 3. Enclose the polyatomic ions in parenthesis if more than one group are required 4. Do not write a subscript of 1 , the presence of the symbol is sufficient. 5. If necessary divide the subscript with a common factor to give the lowest whole number ratio. Examples: Ca+2 + Cl- → CaCl2 1(+2) + 2(-2) = 0  Al+3 + Cl- → AlCl3 Ca+2 + SO4-2 → CaSO4 NAMING IONIC COMPOUNDS FOR BINARY IONIC COMPOUNDS – POSITIVE ION HAS A CONSTANT CHARGE Binary compound – a compound in which two only elements are presents. Binary ionic compound – an ionic compound in which one element present is a metal and the other element present is a nonmetal. The metal is always present as the positive ion and the nonmetal present as the negative ion. Rule: Full name of the metallic element is given first, followed by a separate word containing the stem of the nonmetallic element name and change the ending letters with the suffix –ide. Example: NaF – Sodium Fluoride BaCl2 - Barium Chloride POSITIVE IONS WITH A CONSTANT CHARGE + : All Group IA elements, Ag +2 : All Group IIA elements, Zn, Cd +3 : Aluminum NAMING IONIC COMPOUNDS FOR BINARY IONIC COMPOUNDS – POSITIVE ION HAS A VARIABLE CHARGE TWO WAYS OF NAMING: 1. The stock system of naming 2. Traditional naming RULE:  1. STOCK SYTEM OF NAMING: Name the metallic element or positive ion, write and enclosed in a parenthesis the charge of positive ion in roman numeral first, followed by a separate word containing the stem of the nonmetallic element name and change the ending letters with the suffix –ide Example: FeCl3 - Iron (III) Chloride 2. TRADITIONAL NAMING Use the root name of the metallic element or the positive ion followed by ous ending for the element with a lower charge or use the ic ending for the element with the higher charge. Example: FeCl3 - Ferric Chloride POSITIVE IONS WHOSE CHARGES VARY Stock System Root Name Copper I or Copper II Cupr Mercury I or Mercury II Mercur Gold I or Gold III Aur Iron II or Iron III Ferr Manganese II or ManganeseIII Mangan Cobalt II or Cobalt III Cobalt Nickel II or Nickel III Nickel Chhromium II or Chromium III Chrom Lead II or Lead IV Plumb Tin II or Tin IV Stann Cerium III or Cerium IV Cer Arsenic III or Arsenic V Arsen Antimony III or Antimony V Antimon Bismuth III r Bismuth V Bismuth NAMING IONIC COMPOUNDS CONTAINING POLYATOMIC IONS Positive Ion has a constant charge Rule : Full name of the positive ion (can be a monoatomic or polyatomic ion) is given first, followed by the name of the negative ion (polyatomic ion) Example: NaNO3 - sodium nitrate NH4OH - ammonium hydroxide Positive Ion has a variable charge Rule: You may use the stock system or traditional name in naming the positive ions followed by the name of the polyatomic ion. NAMING OF MOLECULES Molecules consists of a nonmetal and a nonmetal. RULE: Use the prefix Mono - 1 atoms Di - 2 atoms Tri - 3 atoms Tetra - 4 atoms Penta - 5 atoms Hexa - 6 atoms Hepta - 7 atoms Octa - 8 atoms Nona - 9 atoms Deca -10 atoms Example: CO2 - Carbon Dioxide N2O5 - Dinitrogen Pentoxide CO - Carbon Monoxide NOTE: Do not use prefix mono for the first element , use it only for the second element In using prefixes that end with “a” like tetra , drop the letter a if the beginning of the element start with a vowel. The name of the second element always bear the suffix “ide”. Example: P4O10 - tetraphosphurus decoxide Note: Refer to your periodic table of elements for the list of monoatomic and polyatomic ions. 4. Review Question Differentiate compounds from molecules 5. Problems Name the following substances: 1. SF6 6. FeCl3 2. N2S5 7. Al(OH)3 3. Cr(NO3)3 8. K3PO4 4. PbO2 9. SO3 5. CaCl2 10. CCl4 Write the chemical formula for the following substances: 1. Potassium cyanide 6. Ammonium sulfite 2. Lithium nitrate 7. Carbon disulfide 3. Manganese (III) fluoride 8. Zinc permanganate 4. Dioxygen difluoride 9. Sulfur tetrafluoride 5. Tetraphosphorus hexasulfide 10. Gold (i) chloride 6. Assignment 1. Answer Review question 2. Answer problems 3. Submit your assignment (hardcopy, handwritten on SHORT bond paper).