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Naming Compounds and Writing Formulas

Naming Compounds and Writing Formulas. Ms Titolo – Chemistry 112 Unit VI. Review of terms:. Cation: positive ion formed by losing electrons. Anion: negative ion formed by gaining electrons Monatomic Ion: cation or anion formed from a single atom. Ex: Mg +2 , Na +1

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Naming Compounds and Writing Formulas

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  1. Naming Compounds and Writing Formulas Ms Titolo – Chemistry 112 Unit VI

  2. Review of terms: • Cation: positive ion formed by losing electrons. • Anion: negative ion formed by gaining electrons • Monatomic Ion: cation or anion formed from a single atom. Ex: Mg+2, Na+1 • Polyatomic Ion: group of atoms that form a single charged unit. Ex: CO3-2

  3. Review of terms continued: • Ionic Bonds: bonds formed by the attraction of oppositely charged ions created by the transfer of electrons. Ionic bonds are formed between a metal and non-metal or a bond involving a polyatomic ion. • Covalent bonds: bonds formed by the sharing of electrons between two non-metals or a metalloid.

  4. Types of Compounds • Ionic Compound: chemical compound composed of cations and anions combined so that the total positive and negative charges are equal. Occurs between a metal and non-metal (could be a metalloid) or includes a polyatomic ion.

  5. Covalent Compound: formed by the sharing of electrons and does not involve ions. Occurs between two non-metals or could be a metalloid

  6. Valence electrons and Oxidation Numbers reviewed: • Valence electrons: electrons in the outermost energy level. • Oxidation number is the charge formed when an ion is formed by losing or gaining electrons.

  7. Nomenclature (naming) of ions: • To name a monatomic cation you simply write the elements name and add the word ion. Ex: Mg+2 is a magnesium ion. • To name a monatomic anion you take the elements name, drop the ending and add ide, then add the word ion. Ex: Cl-1 is a Chloride ion.

  8. Oxidation Numbers Cont…. • Oxidation numbers for transition metals cannot be determined by looking at the periodic table. Transition elements form ions in more than one way….can have more than one oxidation number. • Only three transition elements have consistent oxidation numbers that you will need to memorize: Zn+2, Ag+, and Cd+2

  9. Transition elements: • To show the oxidation numbers on transition elements • In addition to transition elements tin and lead…under the metalloid stairstep, need a roman numeral too. • Ex: Cu+ = Copper (I) ion, Cu+2 = Copper (II) ion

  10. Practice Ion Naming: • Take a few minutes and look at the back of page 2 in your handout and fill in the chart at the top right of the page…where it asks for the symbol, formula and oxidation number (charge) for the following…when you are finished we will check your answers.

  11. Naming Binary Ionic Compounds: • Binary ionic compound is any ionic compound that includes only two elements. • Nomenclature (naming) • Combine the names of the two ions. • Always write the cation first and then the anion. • When writing the anion, don’t forget to drop the ending and add -ide.

  12. Naming continued… • Ex. 1 – A name for the combination of Cs+ and Cl- …it would be Cesium Chloride • Ex. 2 – A name for the combination of Ba+2 and O-2… it would be Barium Oxide

  13. Writing Ionic Formulas: • An ionic compound must be combined where the positive and negative charges are equal, and should be in the lowest possible whole number ratio. • Examples: • Na+1 combines with Cl-1 When these two ions combine their charges cancel each other out and are in a 1:1 ratio so the formula is NaCl and the name is Sodium Chloride

  14. Ionic Formulas Examples Cont…. • Ba+2 combines with O-2 When these two ions combine they also have charges that cancel each other out. They are a 1:1 ratio. The formula would be BaO and the name Barium Oxide.

  15. Ionic Formulas Examples Cont…. • Mn+4 combines with O-2. These two ions have charges that do not cancel out. We must find the least common multiple of the number of ions needed to allow the charges to cancel out….You would need 1 Mn+4 to make a + 4 charge and 2 O-2 to make a –4 charge. Therefore the formula is MnO2 and would be named Manganese IV Oxide (the roman numeral is needed to show the charge since Manganese is a transition metal)

  16. Formulas cont… • Superscripts are the charges related to the ion…only used when writing the formula of an ion….not in a compound. • Subscripts are used in formulas to show how many of each element is needed to have a neutral compound. If there is no subscript then it is one.

  17. Subscripts cont… • If you need to add a subscript to a polyatomic ion (need more than one of them) put parenthesis around the ion and the subscript outside. Pb (NO3)4

  18. Practice Ionic Naming and Formulas: • DO NOT WRITE THIS!! • Go the back of the first page of your handout and try to write the formulas and names of the compounds in the sections Ionic compounds – write formulas and Write the names.

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