1. BAN Dihydrogen monoxide! Making Molecules

2. Chemical Nomenclature (ionic compounds) CONVENTIONS Scientists have agreed on a set of rules that govern the naming and formulation of compounds. It is universal! The following pages are a programmed approach to the problem of obtaining either the formula or name of a chemical compound. a)The compound will be formed by combining a metal and a non-metal. The metal portion will always appear first in the name and formula. b)The total number of electrons lost by the metal atom(s) must equal the total number of electrons gained by the non- metal atom(s). (The charge left after an atom gains or loses electrons is called its valence.) c)The symbols for the elements consist of one or more letters. The FIRST is always a CAPITAL LETTER, and the SECOND, if used is always a LOWER CASE LETTER. d)The charge of the ion is always written as a superscript, above and to the right of the symbol for the element. i.e. Na +1, F -1, Ca +2 e) The number of atoms of an element in a compound is written as a SUBSCRIPT, below and to the right of the symbol for the element. (ones, “1” are not used, but are “understood”) i.e. H 2 or O 2

3. The formula of a compound is P 2 O. In this material, the atoms present are phosphorous and oxygen. 2 atoms of phosphorous combine with 3 atoms of oxygen to form a molecule of the compound. What atoms are present in the following compounds? How many atoms of each are involved? H 2 OAlF 3 SnH 4 K 2 S PbOK 3 PO 4 CO AgI

4. f)Brackets are sometimes used to contain groups of atoms (called polyatomic ions). If a number appears to the right and below (subscript) the bracket, the subscript is ONLY multiplied by the atoms appearing inside the brackets. i.e. Al(NO 3 ) 3 This compound contains the following atoms: 1 x Al = 1 atom of aluminum 3 x 1 x N = 3 atoms of nitrogen 3 x 3 x O = 9 atoms of oxygen Which elements are present in the following compounds and how many atoms are there of each? Al 2 (SO 4 ) 3 Mg(OH) 2 (NH 4 ) 3 PO 4 Sb 2 (Cr 2 O 7 ) 5 Mn(C 2 H 3 O 2 ) 4 g)The second word of any chemical name ALWAYS starts with a “lower case” letter. The first word of any chemical name can start with a lower case or capital letter, depending on the context. i.e. Sodium chloride or sodium chloride

5. How to determine the chemical formula of an ionic compound ? A chemical formula includes the symbol and the number of each element in the compound. Example: The chemical formula H 2 O represents a compound with : _____ hydrogen atoms and _____ oxygen atoms. How do we determine the number of each element in a compound?!

6. 1st method: Transfer of electrons  Draw a Lewis diagram of each element found in the compound  Draw arrows to show the exchange of electrons  Add atoms and their exchange of electrons until all of the atoms are stable. Ex 1: sodium and sulfur Ex 2: calcium and fluorine Ex 3: beryllium and phosphorous

7. 2nd Method: Criss-cross  Write each symbol of each atom with the ionic charge just above it.  Cross the ionic charges to use them as subscripts.  Do not write number “1” at any point  Divide the subscripts by the same number when possible (like when you reduce a fraction).

8. ElementsChemical Formula ElementsChemical Formula Li and FCa and Br Na and PMg and O Ca and ClNa and S Be and OBe and C K and SCa and I Mg and BrMg and Si Practice:

9. Binary Compounds Binary compounds are those that contain only TWO elements. FROM FORMULA TO NAME RULE 1: Binary Ionic Compounds: 1.Name the first element in the compound. 2.Name the second element in the compound. You must change the ending of the name to IDE. i.e. AlBr 3 PRACTICE Li 2 O CaCl 2 KI AgBr

10. FROM NAME TO FORMULA Remember: Binary compounds are those that contain only TWO elements. METHOD 1.Put down the symbol for the metal and non-metal 2.Place the charge as superscripts beside the appropriate element 3.Criss-cross the charges (write them now as subscripts) 4.Drop the signs (+ve and -ve) 5.Remove the common factors (usually) 6.Forget about the “1’s” i.e. Sodium oxide Magnesium sulfide PRACTICE Hydrogen iodideAluminum bromide Zinc nitrideChromium oxide Barium sulfidePotassium fluoride Calcium chlorideNickel oxide Silicon carbideSilver sulfide

11. RULE 2 : For compounds with a metal that has MULTIPLE VALENCES Some metals, such as antimony and copper, have more than one possible POSITIVE charge. In a compound, the metal can have only one of the charges listed for that metal. The method we will use to designate the valence of these metals CANNOT be used for elements with only one valence! FROM NAME TO FORMULA Preferred (IUPAC) Method Method: *The roman numeral states the valence of the metal in the compound. *Follow the rules for binary compounds BUT use the valence designated by the roman numeral for the metal. Mercury (I) oxidetin (IV) sulfide PRACTICE Iron (III) fluorideAntimony (v) sulfide Sulfur (VI) oxideArsenic (III) Hydride Phosphorous (v) chlorideLead (II) oxide Manganese (IV) carbideNitrogen (III) hydride Copper (I) iodideMercury (II) carbide

12. RULE 2: For compounds with a metal that has MULTIPLE VALENCES FROM FORMULA TO NAME If the metal portion of a compound has a multiple valence you must obtain the TRUE valence from the formula. 1. Criss-cross the subscripts, and write them now as charges (superscripts). *** Remember that the first element (the metal) has a positive valence, while the second element (the non-metal) has a negative valence*** 2.Check that both the metal and non-metal have the correct valence, and that no common factor has been eliminated. 3.First, name the metal, then use the roman numeral system to state the metal valence in brackets, Thirdly, name the non metal, changing the ending to ide. i.e. CuClSnCl 4

13. Check your answers in my binder!