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Nomenclature

Nomenclature. The language of chemistry. Step 0: Identify the Type of Compound. Look at the left side of the name or formula If the left-most element is a Transition metal, then the compound uses the stock naming system.

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Nomenclature

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  1. Nomenclature The language of chemistry

  2. Step 0: Identify the Type of Compound • Look at the left side of the name or formula • If the left-most element is a Transition metal, then the compound uses the stock naming system. • If the left-most element is a non-metal, then the compound uses the covalent naming system • If the left-most element is either an Alkali, Alkaline, or Boron Family metal (or Ammonium NH4)

  3. Naming Ionic Compounds from the Formula • The name of the element on the left is written unaltered. • If there one element on the right (instead of one of the memorized ions) that element gets the –ide ending. • If there is a polyatomic ion on the right, it keeps it’s name. • No numbers are incorporated into the names.

  4. Predicting Formula from names • Write the symbols of each element (or memorized ions) • Include the charge above the symbols (for single elements, the charges go by column of the periodic table, for polyatomic ions, you have memorized them • Cross the charges and bring them down to subscripts, remove the signs, simplify if possible and don’t show the # 1 • If you are putting a subscript (aside from 1) on a memorized ion, use parentheses.

  5. The Stock System • Applies to Complexes (compounds with coordinate bonds). The left-most element will be a transition metal • Stock-system names include a roman-numeral by after the metal that indicates that metal’s charge. • Stock naming and formula prediction works like Ionic, only with the added feature of the roman numerals.

  6. Stock: From Name to Formula • Write the symbols of each element (or poly atomic ion) • Include the charges above the symbols (for the transition metal, the charge is the roman-numeral. • Simplify the charges if possible, cross them and bring them down.

  7. Stock: Formula to Name • Write the name for the metal on the left • Leave space for the roman numeral • Write the name for the anion (either memorized ion or for one element, it will end in –ide) • Calculate the roman numeral needed to balance all charges. • Roman Numeral = |R’s charge * # of R’s| # of L’s

  8. Covalent Nomenclature • Applies to Molecules (compounds with covalent bonds). The left-most element will be a non-metal. • Covalent names use prefixes to represent subcripts from the formula • The prefixes are….

  9. Covalent: Name to formula • Write the symbols for each element • Turn the prefixes into subscripts • (Do not simplify, even if tempted)

  10. Covalent: Formula to Name • Write the names of each element in the formula • If the left-most element had a subscript of two or more, use the prefix for that subscript (if there was only one of the atoms on the left, don’t use a prefix). • For the element on the right, use prefixes no matter how many or few atoms there are (i.e. mono- through deca)

  11. Mixed review • Step 0: decide which type of compound each example is. • Step 1: name or predict formulae for all covalent compounds (easiest, uses prefixes, no simplifying) • Step 2: name or predict formulae for all ionic compounds (left stays the same, right gets –ide; simplify charges and criss-cross) • Step 3: name & predict all the stock compounds (roman numeral is charge for criss-cross; name L and R elements then calculate roman numeral)

  12. Lewis Structures • Molecules (covalent compounds) form complicated and distinct structures. • We picture what is going on in the structure using lines to represent 2 electron covalent bonds, and pairs of dots to represent “lone-pairs” • Lone-pair electrons are those valence electrons that do not bond. • They still have important consequences for how compounds react, and the shape the molecules take on.

  13. Predicting Lewis Structures 0) Start with the molecule’s formula (predict it from the name if needed) • Tally up all valence electrons • Pick a central atom • Bond other atoms to center (& remove the e-’s used from the tally) *** When all e-’s are used up, and all atoms are happy, the structure is done, which could be after step’s 3, 4 or 5.

  14. 4) distribute from tally the remaining electrons as lone-pairs, starting with the outer atoms and moving to the central atom. 5) Convert lone-pairs into additional bonds. A good structure uses all electrons, and makes every atom happy. In step 5, if you have a choice of where to make the extra-bond, choose a lone pair from the less electronegative atoms, instead of from more electronegative atoms.

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