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Naming Compounds

Naming Compounds. Formulas and Compounds. Compound - a substance made of 2 or more elements joined together in a specific way Chemical Formula- the expression of types and number of atoms of each type in a molecule

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Naming Compounds

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  1. Naming Compounds

  2. Formulas and Compounds • Compound- a substance made of 2 or more elements joined together in a specific way • Chemical Formula- the expression of types and number of atoms of each type in a molecule • Structural Formula- a graphic representation of the molecular structure, showing how the atoms are arranged

  3. Tools for Writing Formulas • 1. Each atom present is represented by its element symbol. • 2. The number of each type of atom is indicated by a subscript written to the right of the element. • 3. When only one atom of given type is present, the subscript 1 is NOT written. (understood)

  4. Problems • 1. A molecule contains four phosphorus atoms and ten oxygen atoms. • 2. A molecule contains one uranium atom and six fluorine atoms. • 3. A compound contains one aluminum atom and 3 chlorine atoms. • Worksheet Examples

  5. Naming Binary Compounds

  6. There are more than 4 million chemical compounds known. Memorizing the common names of all these would be impossible. • SOLUTION: a system for naming compounds in which the name tells something about the composition of the compound

  7. Naming Compounds That Contain Metal and a Nonmetal • Binary Ionic Compound- a 2 element compound consisting of a cation and an anion RULES • cation (+) is always written 1st • cationtakes the name from the name of the element. Ex: Na+ is called sodium • anion (-) is written second • anion take the first part of the element name and adding –ide. Ex: Cl- ion is chloride

  8. TYPE 1 CATIONS • Def. metal ions that only form one type of cation • Ex: Na always forms Na+ Cs always forms Cs+ Ca always forms Ca2+ Al always forms Al3+ • Type 1 Cations form Type 1 Binary Compounds • Type 1 Compounds- def. the metal present form only one type of cation

  9. EXAMPLES • Ex: NaI Sodium iodide • Na+ = sodium cation • I- = iodine anion • CaO Calcium Oxide • Ca2+ = calcium • O2- = oxide

  10. TYPE 2 CATIONS • Def. metal ions that can form 2 or more cations • Ex: Cu Cu+ & Cu2+ • *Type 2 Cation form Type 2 Binary Compounds • Type 2 Compounds- def. the metal present can form 2 or more cations that have dif charges

  11. Type IIBinary Ionic Compounds • Group 1A and 2A metals are always Type I Cations • Transition metals are almost always Type 2 Cations Gold Chloride • PROBLEM: • Au -> can form +1 and +3 • Cl -> forms -1 • Au+ and Cl- = AuCl • Au3+ and Cl- = AuCl3 • Chemists decided to deal with this problem by using a Roman numeral to specify the charge on the cation. The Roman numeral tells the charge on the ion, not the number of ions present in the compound. • 1 = I 2 = II 3 = III 4 =IV 5 = V

  12. EXAMPLES • FeCl2 • Fe? + 2Cl- • ? (+) +2(1-) = 0 • 2+ + 2- = 0 • So the charge of Fe = 2+ • Called Iron (II) Chloride

  13. FeCl3 • Fe?+ 3Cl- • ?(+) +3(1-) = 0 • 3+ + 3- = 0 • So the charge of Fe = 3+ Called Iron (III) Chloride • PbO2 • Pb?+ 2O2- • ?(+) +2(2-) = 0 • 4+ + 4- = 0 • So the charge of Pb = 4+ Called Lead (IV) Oxide

  14. Compounds with Complex Ions • Not all compounds are binary • Some composed of more than 2 elements Polyatomic Ion  a positively or negatively charged, covalently bonded group of atoms composed of 2 or more elements

  15. Writing Names • 1. Write the name of the positive ion. • 2. Write the name of the negative ion. Ex: K2SO4 potassium sulfate Ex: Sr(OH)2 strontium hydroxide

  16. Writing Formulas • 1. Write the name of the positive ion. • 2. Write root name of the negative ion. • 3. Balance the charges to make it a neutral compound. • Ex: Ammonium phosphate ammonium: NH4+1 phosphate: PO4-3 (NH4)3PO4

  17. Naming Binary Covalent Compounds • Formed between nonmetals • Use prefixes to tell how many atoms of each element are present • *OMIT mono- on the first element written CO Carbon monoxide, not monocarbonmonoxide • -ide ending • NO Nitrogen monoxide • NO2 Nitrogen dioxide • N2O5 Dinitrogenpentoxide • *Sometimes an –a or –o is dropped for pronunciation.

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