1 - Nomenclature

1 - Nomenclature - Chem 127 Chemical Nomenclature...

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Chem 127 Chemical Nomenclature Nomenclature is essential to our understanding and use of chemistry. Summarized below are the basic rules you should learn for naming chemical compounds. You should also read about this in Chapter 2 of your text. Note that this will NOT be covered in any detail in lecture, so you need to work on this on your own or in groups. YOU MUST LEARN THESE RULES or you will find yourself lost and hurting for the entire term. See me for clarification and assistance. Naming Ionic Compounds - Ionic compounds are formed between metal and nonmetal Ionic compounds are named by first identifying the positive ion (the cation) and then the negative ion (the anion). You should note that the cation is always the metal and the anion the nonmetal. The positive ion takes the same name as its element, the negative ion takes the first part of its element name plus an -ide ending. Thus given the following formulas, we would name the compounds accordingly: Ca 3 P 2 Calcium phosphide MgSe Magnesium selenide Na 2 O Sodium oxide To write a formula from a given name, you simply take the symbols for the named elements and combine them in a ratio that gives you a neutral ionic compound. That means that the charges must balance, so you have to do a little figuring as to what ions the elements will form and how many of each you'll need to balance out positive and negative charges. The number of each element present is shown as a subscript after the element symbol. Example: Calcium bromide: Ca would form a +2 ion, and Br a -1 ion. Thus to have a neutral compound, you need 2 Br for every 1 Ca The formula would be CaBr 2 You must know the names and charges of all monatomic ions listed on the separate handout! Compounds with metals that can form more than one ion Several transition metals can form more than one ion. For systematically named compounds for the metals that can form more than one ion, the charge on the metal will be indicated in the given name by a Roman numeral in parentheses. Thus you can easily determine the corresponding formula. For example, iron can form either a +2 or a +3 ion, an example of a compound of the +3 ion is given below:
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1 - Nomenclature - Chem 127 Chemical Nomenclature...

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