Naming Compounds and Writing Formulas

Step 1 - Determine the Bond Type Metal atomsNon-metal atoms Metallic bondsIonic bondsCovalent bonds Ionic bonds – Form between metal and a non-metal atoms. Forms ions, not molecules. Covalent bonds – Form between 2 non-metals. Forms molecules. Metallic bonds – Mixture of 2 metal atoms.

Naming Ionic Compounds 1.Name the first ion 2.Name the second ion changing the suffix to –ide. Examples: NaCl Sodium Chloride Calcium CaCl 2 Chloride MgI 2 Magnesium iodide

Practice KF MgI 2 AlCl 3 GaF 3 potassium fluoride magnesium iodide gallium fluoride aluminum chloride

Writing Ionic Formulas Two simple steps: 1.Write the symbol and charge of each ion 2.Balance the charges using subscripts. – What is the number of valence electrons? – What is the charge on the ION? Magnesium chloride Mg +2 Cl -1 Cl -1 MgCl 2 Write the symbol and charge of each ion. Balance the charges by supplying subscripts. Subscripts tell how many of each atom is present. You need a second Cl -1 to balance the charges

Aluminum SulfideWrite the symbol and charge of each ion. Al +3 S -2 Balance the charges by supplying subscripts. In this case the charges do not evenly divide into each other. You must find the least common multiple. SIX How many aluminums are needed to arrive at a +6 charge? How many sulfurs are needed to arrive at a -6 charge? 2 3 Al +3 S -2 Al 2 S 3

Practice magnesium oxide lithium bromide aluminum chloride sodium oxide MgO LiBr AlCl 3 Na 2 O

Polyatomic ions Polyatomic ion – Group of atoms that act as a unit and carry a charge. CO 3 -2 carbonate This ion is composed of one carbon and three oxygens and the entire group has a charge of -2.

Some Polyatomic Ions SO 4 -2 Sulfate SO 3 -2 Sulfite ClO 4 -1 Perchlorate ClO 3 -1 Chlorate ClO 2 -1 Chlorite ClO -1 Hypochlorite PO 4 -3 Phosphate C 2 H 3 O 2 -1 Acetate OH -1 Hydroxide NO 3 -1 Nitrate NO 2 -1 Nitrite You need to recognize these!!! NH 4 +1 Ammonium (only positive PI) More examples:

How to Name Ionic Compounds with Polyatomic Ions 1.Name the first ion. 2.Name the polyatomic ion. – You just have to look up the polyatomic ion on your sheet. Na 2 CO 3 Sodium carbonate Carbonate When you look at this compound you should recognize that this is NOT binary. There are THREE elements present. When you see this, immediately look for a polyatomic ion. Carbonate is present here.

NH 4 ClName the first ion. AmmoniumName the second ion. chloride Notice that since the second ion is a nonmetal, the suffix changes to –ide. (NH 4 ) 3 PO 4 Name the first ion. Name the second ion. Ammoniumphosphate Looks like a monster, but it’s really a pussycat.

How do you write formulas for ionic compounds with polyatomic ions? Very much like writing formulas for Binary Ionic Compounds. Two steps: Write the formulas/symbols of each ion. Balance the charges by using subscripts. If a subscript is needed for a polyatomic ion, it must be put in parentheses with the subscript on the outside. Let’s do some!!

Aluminum nitrateFirst, you can tell from the name that there is a polyatomic ion present (nitrate). All binary ionic compounds have suffixes of –ide. Write the formula/symbol and charge of each ion. Al +3 NO 3 -1 Balance the charges by supplying subscripts. Since Al is +3 and NO 3 is -1, you need a total of 3NO 3 -1 to balance one Al +3 Since you will need a subscript of 3 for NO 3 -1, you need to put this in parentheses with the 3 outside. Al(NO 3 ) 3

Silicon acetateWrite the formula/symbol and charge of each ion. Si +4 C 2 H 3 O 2 -1 Balance the charges by supplying subscripts. Since Si is +4 and C 2 H 3 O 2 is -1, you will need 4 C 2 H 3 O 2 -1 to balance 1Si +4 Si(C 2 H 3 O 2 ) 4 Calcium phosphate Write the formula/symbol and charge of each ion. Balance the charges by supplying subscripts. Since Ca is +2 and PO 4 is -3, you will need 3 Ca+2 to balance 2 PO 4 -3 Ca +2 PO 4 -3 Ca 3 (PO 4 ) 2

Covalent Compounds What are Binary Molecular Compounds? These compounds contain two elements (binary). The term “molecular” indicates that these elements are joined by a covalent bond. They must therefore be nonmetals. Bottom line – 2 elements – both nonmetals To name and write formulas for these, you must know some numerical prefixes.

Naming Covalent Compounds – you must use prefixes. 1 = mono3 = tri 5 = penta 7 = hepta 9 = nona 2 = di4 = tetra 6 = hexa 8 = octa 10 = deca 1.The first nonmetal only gets a numeric prefix when there is more than one. No prefix if there is only one. 2.The second element always gets a numeric prefix and always has a suffix of -ide

CO 2 Carbon dioxide CO Carbon monoxide N2O4N2O4 Dinitrogen tetraoxide H2OH2O Dihydrogen monoxide CCl 4 Carbon tetrachloride Name the first element. Since there is only one, no prefix is needed. The second element always gets a prefix and a suffix of – ide. Name the first element. Since there are two present, the prefix “di” is needed. The second element always gets a prefix and a suffix of –ide. Do you think it wise to BAN DHMO?

AlCl 3 What do you think about this one??? Be careful. This is a metal and nonmetal. Always keep your Periodic Table in front of you for reference. You may have been tempted to say “aluminum trichloride”. This is INCORRECT! This is a binary IONIC compound. No prefixes are used. Simply aluminum chloride. Given the names of binary molecular compounds, how do you write the formulas? Very easy to do!!! The prefixes tell you how to write the formulas. DO NOT CONSIDER CHARGES. NONMETALS ARE ALL NEGATIVE SO TO USE CHARGES DOES NOT WORK!

Silicon dioxide Diphosphorous pentachloride Silicon and oxygen are both nonmetals. The lack of a prefix on silicon means that there is only ONE silicon. The prefix “di” in front of oxide means that there are TWO oxygens. SiO 2 Phosphorous and chloride are both nonmetals. The prefix “di” means that there are TWO phosphorouses (Is that a word?) The prefix “penta” before chlorine means that there are five chlorines. P 2 Cl 5

NO Nitrogen monoxide Nitrogen and oxygen are both nonmetals. The lack of a prefix on nitrogen means only ONE nitrogen. The prefix “mono” on oxygen indicates ONE oxygen. Isn’t this sooooooo easy!??

Name the following compounds. PH 3 CO HI N 2 O 3 phosphorous trihydride carbon monoxide hydrogen monoiodide dinitrogen trioxide