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Unit 3-6 covalent compounds

Unit 3-6 covalent compounds. F. F. ••. ••. ••. •. •. ••. F. F. ••. •. •. •. •. H. H. O. ••. ••. ••. ••. ••. ••. ••. ••. ••. F. F. ••. H. H. ••. O. ••. ••. ••. Single Covalent Bonds. two atoms share a pair of electrons 2 electrons

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Unit 3-6 covalent compounds

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  1. Unit 3-6 covalent compounds

  2. F F •• •• •• • • •• F F •• • • • • H H O •• •• •• •• •• •• •• •• •• F F •• H H •• O •• •• •• Single Covalent Bonds • two atoms share a pair of electrons • 2 electrons • one atom may have more than one single bond

  3. •• •• • • • • O O •• •• •• •• O •• •• •• •• O Double Covalent Bond • two atoms sharing two pairs of electrons • 4 electrons

  4. •• •• • • • • N N • • N N •• •• •• •• •• Triple Covalent Bond • two atoms sharing 3 pairs of electrons • 6 electrons

  5. Nomenclature of Binary Molecular Compounds • Write name of first element in formula • element furthest left and down on the Periodic Table • use the full name of the element • Writes name the second element in the formula with an -ide suffix • as if it were an anion, however, remember these compounds do not contain ions! • Use a prefix in front of each name to indicate the number (the subscript) of atoms • Neveruse the prefix mono- on the first element

  6. Subscript - Prefixes • 1 = mono- • not used on first nonmetal • 2 = di- • 3 = tri- • 4 = tetra- • 5 = penta- • 6 = hexa- • 7 = hepta- • 8 = octa- • 9 = nona- • 10 = deca- • drop last “a” if name begins with vowel

  7. Example – Naming Binary MolecularBF3 • Name the first element boron • Name the second element with an –ide fluorine  fluoride • Add a prefix to each name to indicate the subscript monoboron, trifluoride • Write the first element with prefix, then the second element with prefix • Drop prefix mono from first element boron trifluoride

  8. Name the following • NO2 • PCl5 • I2F7 • nitrogen dioxide • phosphorus pentachloride • diiodine heptafluoride

  9. Example – Write formula ofdinitrogenpentoxide • Identify the symbols of the elements nitrogen = N oxide = oxygen = O • Write the formula using prefix number for subscript di = 2, penta = 5 N2O5

  10. Write formulas for the following • dinitrogentetroxide • sulfur hexafluoride • diarsenictrisulfide • N2O4 • SF6 • As2S3

  11. Acids – a special kind of covalent compound • acids are molecular compounds that form H+ when dissolved in water • to indicate the compound is dissolved in water (aq) is written after the formula • NOT acid if not dissolved in water • sour taste • dissolve many metals – based on metal activity series • like Zn, Fe, Mg; but not Au, Ag, Pt • formula generally starts with H • e.g., HCl, H2SO4

  12. Reaction of Acids with Metals H2 gas

  13. Acids • Contain H+1cation and anion • in aqueous solution • Binary acids have H+1cation and nonmetal anion • Oxyacids have H+1cation and polyatomic anion Tro, Chemistry: A Molecular Approach

  14. Nomenclature of Binary Acids (HX) • write a hydro prefix • follow with the nonmetal name • change ending on nonmetal name to –ic • write the word acid at the end of the name

  15. Example - Naming HCl • Identify the anion Cl = Cl-, chloride because Group 7A • Name the anion with an –ic suffix Cl- = chloride  chloric • Add a hydro- prefix to the anion name hydrochloric • Add the word acid to the end hydrochloric acid

  16. Naming Oxyacids • if polyatomic ion name ends in –ate, then change ending to –icsuffix • if polyatomic ion name ends in –ite, then change ending to –oussuffix • write word acidat end of all names

  17. Example – Naming OxyacidsH2SO4 • Identify the anion SO4 = SO42- = sulfate • If the anion has –ate suffix, change it to –ic. If the anion has –ite suffix, change it to -ous SO42- = sulfate  sulfuric • Write the name of the anion followed by the word acid sulfuric acid (kind of an exception, to make it sound nicer!)

  18. Example – Naming OxyacidsH2SO3 • Identify the anion SO3 = SO32- = sulfite • If the anion has –ate suffix, change it to –ic. If the anion has –ite suffix, change it to -ous SO32- = sulfite  sulfurous • Write the name of the anion followed by the word acid sulfurous acid

  19. Name the following • H2S • HClO3 • HNO2 • hydrosulfuric acid • chloric acid • nitrous acid

  20. Homework • Handout case 4-5

  21. Writing Formulas for Acids • when name ends in acid, formulas starts with H • write formulas as if ionic, even though it is molecular • hydro prefix means it is binary acid, no prefix means it is an oxyacid • for oxyacid, if ending is –ic, polyatomic ion ends in –ate; if ending is –ous, polyatomic ion ends in –ous

  22. Example – write formula of hydrosulfuricacid • Write the symbol for the cation and its charge • Write the symbol for the anion and its charge • Charge (without sign) becomes subscript for other ion • Add (aq) to indicate dissolved in water • Check that the total charge of the cations cancels the total charge of the anions in all acids the cation is H+ H+ hydro means binary S2- H+ S2- H2S H2S(aq) H = (2)∙(+1) = +2 S = (1)∙(-2) = -2 Tro, Chemistry: A Molecular Approach

  23. Example – Oxyacidscarbonic acid • Write the symbol for the cation and its charge • Write the symbol for the anion and its charge • Charge (without sign) becomes subscript for other ion • Add (aq) to indicate dissolved in water • Check that the total charge of the cations cancels the total charge of the anions in all acids the cation is H+ H+ no hydro means polyatomicion CO32- -ic means -ate ion H+ CO32- H2CO3 H2CO3(aq) H = (2)∙(+1) = +2 CO3 = (1)∙(-2) = -2

  24. Example – Oxyacidssulfurous acid • Write the symbol for the cation and its charge • Write the symbol for the anion and its charge • Charge (without sign) becomes subscript for other ion • Add (aq) to indicate dissolved in water • Check that the total charge of the cations cancels the total charge of the anions in all acids the cation is H+ H+ no hydro means polyatomicion SO32- -ous means -ite ion H+ SO32- H2SO3 H2SO3(aq) H = (2)∙(+1) = +2 SO3 = (1)∙(-2) = -2 Tro, Chemistry: A Molecular Approach

  25. Practice - What are the formulas for the following acids? • chlorous acid • phosphoric acid • hydrobromic acid • H+ with ClO2–HClO2 • H+ with PO43–H3PO4 • H+ with Br–HBr

  26. Hydrate CoCl2∙6H2O Anhydrous CoCl2 Hydrates • hydrates are ionic compounds containing a specific number of waters for each formula unit • water of hydration often “driven off” by heating • in formula, attached waters follow ∙ • CoCl2∙6H2O • in name attached waters indicated by suffix -hydrate after name of ionic compound • CoCl2∙6H2O = cobalt(II) chloride hexahydrate • CaSO4∙½H2O = calcium sulfate hemihydrate

  27. Practice • What is the formula of magnesium sulfate heptahydrate? • What is the name of NiCl2•6H2O? • MgSO47H2O • nickel(II) chloride hexahydrate

  28. Homework • Handout: the case 2,3 and 6.

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