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Formula writing

Formula writing. IONS. Cation ion – usually metals positive ion (+) loses electrons Anion ion – usually nonmetals negative ion (-) gainies electrons. Ionic Compounds - transfer of electron(s). Ionic compound must be neutral (total + = total -) Write symbol of each ion

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Formula writing

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  1. Formula writing

  2. IONS Cation ion – usually metals positive ion (+) loses electrons Anion ion – usually nonmetals negative ion (-) gainies electrons

  3. Ionic Compounds- transfer of electron(s) Ionic compound must be neutral (total + = total -) • Write symbol of each ion • See if the charges balance out If yes, write formula If no, then criss-cross number (ONLY) of charges (lowest whole number ratio) Sodium chloride calcium chloride Na + Cl - Ca 2+ Cl 1- Same (1+ = 1-) 2+ = 1- NaCl CaCl2 We do not show 1’s in formulas

  4. More examples Sodium oxide calcium nitrate Aluminum sulfate iron (III) chloride You need the () since your ion contains more than one element and you need 2 or more of them to balance the formula Na 1+ O 2- Ca 2+ NO31- Ca(NO3)2 Na2O Al 3+ SO42- Fe 3+ Cl 1- Transition metals will usually have roman numerals. They tell you the CHARGE of the cation FeCl3 Al2(SO4)3

  5. Nomenclature of ionics(naming) • Id the cation. • Ask if it is a transition metal, Sn, or Pb? -If no then just name each ion. -If yes, then name each ion leaving a space after the cation for roman numerals. CaCl2FeCl2 See next slide on how to determine the roman numeral Iron ( ) chloride Calcium chloride

  6. How to figure out the charge of the cation? Remember the total number of positives must equal the number of negatives. We know the charge of the anion, so do the math. FeCl2 So what charge must the Fe have to cancel out the 2-’s? Cl 1- 2+ Fe Cl 1- Therefore it is iron (II) chloride. The roman numeral tells us the charge on the iron.

  7. Let’s try some more. Co(NO3)3 Ni2(SO4)3 What is the charge for each anion? 2- 1- How many anions are present? 3 3 Total number of negatives (1-)(3) =3- (2-)(3)=6- What charge must the cation have to cancel the negatives out? 3+ = 3- 6+ = 6- Charge of cation (6+)/2= 3+ 3+ Name of each ionic compound Nickel(III) sulfate Cobalt(III) nitrate

  8. Molecular compounds Contains all nonmetals and use prefixes Mono- 1 (used sparingly with oxygen) Di – 2 tri -3 tetra – 4 penta- 5 Hexa – 6 hepta – 7 octa – 8 nona – 9 Deca- 10 Nitrogen trichloride diphosphorus tetraoxide P2O4 NCl3

  9. Acids – Contain H’s listed first Remember the following Focus on anion and then add appropriate number of H’s Binary acid (HX) only 2 elements Hydro--ic acid Tertiary acid (3 elements) Hypo- -ite  hypo- -ous acid -ite  -ous acid -ate  -ic acid Per- -ate  per- -ic acid Remember you ate it and it tasted icky

  10. Naming and formula writing for acids H2SO4 H2CO2 HF Nitric acid sulfurous acidhydrochloric acid Sulfate so the –ate becomes -ic Carbonite so the –ite becomes -ous Binary so hydro--ic acid Sulfuric acid Hydrofluoric acid Carbonous acid nitrate sulfite H 1+ NO31- H 1+ SO32- H 1+ Cl 1- HNO3 H2SO3 HCl

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