Writing Chemical Formulas and Naming Chemical Compounds

Lesson #5 – Naming Metal-Non-Metal Compounds Words for your glossary: Chemical Formula Valence Binary Compound Zero Sum Rule Polyatomic Ion

The Language of Chemistry http://www.youtube.com/watch?v=q2s8hQ5NIpE&feature=related It’s like learning a new language You will learn to take the name of a compound and then find it’s formula Eg. Carbon dioxide = CO2 You will also learn to translate a formula into words Eg. MgCl2 becomes magnesium chloride. There are three main patterns: naming ionic compounds, polyatomic ions, and covalent compounds.

Chemical Formulas Provides two important types of information: 1. ________________________________________________________________ 2. The number of atoms of each element that are present in a compound. Tip: __________________________________________________ Eg. Ca + Br (pp.95 in text)

What a chemical formula represents In covalent compounds: how many of each type of atom are in the molecule Eg. NH3 In Ionic compounds: ______________________________________________ Eg. MgO Remember that ionic compounds are found in a lattice structure so in MgO, the atoms exist in a 1:1 ratio, held together by ionic bonds.

Valence Numbers Valence: __________________________________________________________________________________________________ Eg. Group 1 elements have the capacity to lose one e- in order to bond. They have a valence of +1. Some larger elements have 2 or more valence numbers. Table 3.3, pp. 97.

Naming Compounds That Contain a Metal and a Nonmetal Binary ionic compounds contain ___________ _____________________________________ Type I compounds Metal present forms only one cation Type II compounds Metal present can form 2 or more cations with different charges

Naming Compounds That Contain a Metal and a Nonmetal

Naming Ionic Compounds Type I Binary Ionic compounds

Naming Compounds That Contain a Metal and a Nonmetal For compounds containing both a metal and a nonmetal, ____________________________The nonmetal is named from the root element name.

Cations with 2 or more Valences Type II Binary Ionic compounds Since the metal ion can have more than one charge, a ________________________is used to specify the charge. Outlined in your text as the Stock System (pp.103, table 3.6)

Common multi-valent cations Type II Binary Ionic compounds

Polyatomic ions are charged entities composed of several atoms bound together. They have special names and must be memorized.

Polyatomic Ions YOU need to know Chlorate Nitrate Carbonate Sulfate Phosphate Ammonium Hydroxide

Naming ionic compounds containing polyatomic ions follows rules similar to those for binary compounds. ammonium acetate

Polyatomic Ions ____________________________________ “poly” means “many” or “lots” in Greek __________________________________ Remain unchanged in simple reactions because of _________________________ They behave like a single unit and should be treated as a ______________________ The most common is NH4+ - Ammonium Table 3.4 pp. 98

Writing Chemical Formulas Using Valences Zero Sum Rule: Eg. KF = the sum of the valences is O What if you have compound that has multi-valent ions?

Cross-Over Rule Cross Over Rule lets you balance the equations. Pp.99 in your text. Let’s take Mg – Cl 1. Write the unbalanced formula (metals first) 2. Add the valence numbers 3. Cross over numbers 4. Check the subscripts (reduce or remove any valences of 1)

Practice! Sodium Sulphide Aluminum Sulphide Calcium Oxide Calcium Phosphide

Crossing Over with Polyatomic Ions Metal + Polyatomic Ion: Eg. K – PO4 (potassium phosphate) 1. Write unbalanced formula. Put brackets around the polyatomic ion (s) 2. Write in the valences 3. Cross over, write in the subscripts 4. Tidy up: get rid of 1s, if needed, get rid of the brackets.

Poly on Poly Try Ammonium Phosphate! What about Ammonium Sulphate?

Putting it all together To name a binary compound (2 elements) which is ionic, write the metal first and the non-metal ending in –ide Eg. Potassium Bromide If there is an alternate valence, use the stock system when naming the compound. Eg. Lead (II) oxide (Pb2+ + O) Conversely, use the cross over rule to find the chemical formula of a compound.

One side note…. Naming compounds that contain Hydrogen Can be the first name / least EN Eg. HCI – Hydrogen chloride OR can be more EN Eg. Sodium hydride or lithium hydride. Many compounds that contain H are acids. We will discuss this later………..

Copy the following table and fill in the correct formula or name for each of the compounds listed: Al2O3 MgBr2 Potassium oxide Ag2S Manganese ( VII) oxide PbCl2 Calcium oxide Copper (II) chloride BaCl2 Ferric Phosphide

Lesson #6 – Naming compounds with polyatomic ions

Pattern! ClO- : hypochlorate ClO2- : chlorite ClO3- : chlorate ClO4- : perchlorate Can YOU see it?

Table 3.7 – Meaning of prefixes and suffixes (pp.105) Prefix and Suffix Number of oxygen atoms HYPO ___________________ITE X -2 OXYGEN ATOMS ___________________ITE X-1 OXYGEN ATOMS ___________________ATE X OXYGEN ATOMS PER ___________________ATE X+1 OXYGEN ATOMS

Really? Yes, Really! http://www.youtube.com/watch?v=Jp5yblKmQQI&feature=related

Practice, Practice, Practice!! Let’s do #23 on pp. 105 together! Make sure you do the homework for these two lessons. The only way to be good at this stuff is to do LOTS of examples! Pp. 19 in your green book! Make sure you do your readings for lessons 6&7 for Monday!