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Lesson Objectives Write formulas for Common polyatomic ions Ionic Compounds

Lesson Objectives Write formulas for Common polyatomic ions Ionic Compounds Containing main group or transition metals Bases Acids Binary acids Oxyacids Covalent compounds. Writing Formulas. Formulas express the types and numbers of atoms in a compound

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Lesson Objectives Write formulas for Common polyatomic ions Ionic Compounds

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  1. Lesson Objectives • Write formulas for • Common polyatomic ions • Ionic Compounds • Containing main group or transition metals • Bases • Acids • Binary acids • Oxyacids • Covalent compounds • Writing Formulas

  2. Formulas express the types and numbers of atoms in a compound • Symbols are used to represent the types of elements • Subscripts are used to represent the number of atoms of each element • Chemical Formulas Ex) NH3 N H H H

  3. Ionic formula– shows the number and types of ions in a formula unit • Formula unit – the lowest whole number ratio of ions in a compound • Has no overall charge • Ionic Formulas Ex) NaCl Formula unit

  4. Molecular formula – a formula that shows the number of atoms of each element in a molecule • Does not contain ions • Formulas for Covalent Compounds Ex) H2O2 H O O H

  5. Least electronegative element is written first • Prefixes in the name determine the number of atoms of each element in the compound • Writing Molecular Formulas

  6. Number of atoms will become the subscript • No prefix on the first element’s name means there is one atom of the element • 1’s are not written in formulas • Writing Covalent Formulas • O2 • N Ex) Nitrogendioxide =

  7. Writing Ionic Formulas • Determine the charges of the ions in the formula • Generally, charge can be determined by an ion’s group number 1+ Group 1A 3+ 2- 1- Group 8A 2+ 3- Group 2A Group 3A Group 4A Group 5A Group 6A Group 7A

  8. Determine the charges of the ions in the formula • Exceptions — multiple oxidation state metals • Most transition and post transition metals can form more than one cation • Oxidation state will be written in the name as a Roman numeral • Writing Ionic Formulas Ex) Iron(II) = Fe2+

  9. Write ions with charges • Cations written first • Cross anddrop charges • Use the absolute value of each ion’s charge as the subscript for the other ion • Reduce subscripts to the lowest whole number ratio Ex) Write the formula for lead(IV) oxide Step 2: Pb4+ O-2 Step 3: Pb2O4 Step 4: PbO2 • Writing Ionic Formulas The charges of the ions balance each other so the overall charge is zero.

  10. Write ions with charges • Cations written first • Cross and drop charges • Use the absolute value of each ion’s charge as the subscript for the other ion • Reduce subscripts to the lowest whole number ratio Ex) Write the formula for lead(IV) oxide Step 4: PbO2 • Writing Ionic Formulas Pb4+ O2- O2- (1 × +4 ) + (2 × –2) = 0 The charges of the ions balance each other so the overall charge is zero.

  11. Write the correct formula for iron (III) oxide Fe3+ O2- Fe2O3

  12. Follow the same basic steps for ionic formulas with polyatomic ions • You will have a list of polyatomic ions to refer to • Ionic Formulas with Polyatomic Ions

  13. When more than one of a particular polyatomic ion is present, parentheses are needed • Parentheses go around the entire formula of the polyatomic ion with the subscript outside parentheses • Subscript describes the number of polyatomic ions • Ionic Formulas with Polyatomic Ions Ex) Ammoniumcarbonate NH4+ CO32- (NH4)2CO3

  14. Write the correct formula for magnesium phosphate Mg2+ PO43- Mg3(PO4)2

  15. Some ionic compounds are bases • Bases are usually composed of a cation and the polyatomic ion hydroxide cation + hydroxide • Formulas of these bases are written using the same rules as other ionic compounds with polyatomic ions • Formulas for Bases Ex) Mg(OH)2

  16. Oxyanions are named in series • Oxyanion – polyatomic ion that includes oxygen • Naming pattern most common ion nonmetal’s stem + -ate • Number of oxygen atoms in the most common ion will depend on the nonmetal • Look up or memorize the formulas of -ate ions • All of the formulas in the series can be determined if one of the formulas from the series is known • Patterns in Polyatomic Ion Formulas

  17. Each oxyanion in the series will have a different number of oxygen atoms • Prefixes and suffixes attached to the nonmetal stem designate the ion’s place in the series • Patterns in Polyatomic Ion Formulas Ex) O4 O3 O2 O

  18. Prefixes and suffixes organized by the number of oxygen atoms present in the formula per-…-ate > -ate > -ite> hypo-…-ite • Formulas for Oxyanions O4 O3 O2 O5 Ex) Phosphate= PO43– What is the formula for perphosphate? PO53– What is the formula for phosphite? PO33– What is the formula for hypophosphite? PO23–

  19. Formulas begin with H • Type of acid is determined by its anion • Binary acid – acid composed of hydrogen ions and monatomic anions H+ + monatomic anion • Oxyacid– acid composed of hydrogen ions and oxyanions H+ + oxyanion • Formulas for Acids Ex) hydrochloric acid = HCl Ex) chloric acid = HClO3

  20. Names that have the hydro- prefix and the -icsuffix are binary acids • Find the formula by treating it as if it were an ionic compound • Formulas for Binary Acids Ex) hydrochloric acid = HCl Ex) hydrosulfuric acid = H2S

  21. Names with the following combinations of prefixes and suffixes are oxyacids: per-…-ic> -ic> -ous> hypo-…-ous • The type of oxyacid is determined by its anion per-…-ate > -ate > -ite> hypo-…-ite • Formulas for Oxyacids Ex)

  22. Formulas for Oxyacids Ex) What is the formula for sulfuric acid? per-…-ic> -ic> -ous> hypo-…-ous per-…-ate > -ate > -ite> hypo-…-ite -ic -ate SO42- H2SO4

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