Formulas and Nomenclature (Naming)

Review: Ionic compounds The simplest ionic compounds form between a metal and a nonmetal. Metal atoms lose electrons and become + charged ions called cations. Nonmetal atoms gain electrons and become – charged ions called anions.

Binary Only has 2 different elements If you are describing a “binary ionic compound”, it will have one metallic element and one nonmetallic element

Monovalent (also called type 1) metals Used to describe metals that can only form one ion Monovalent metals are: Group 1 alkali metals – always form +1 cation Group 2 alkaline earth metals – always form +2 cation Aluminum – always forms +3 cation Zinc and Cadmium – always form +2 cation Silver – always forms +1 cation *AZCA *stair-step on periodic table

Monovalent metals

charge = oxidation number* *this is only true in ionic compounds Group 1 metals have an oxidation number of +1 Group 2 metals have an oxidation number of +2 Al has an oxidation number of +3 Zn and Cd have an oxidation number of +2 Ag has an oxidation number of +1 practice

Writing Names for Binary Ionic Compounds with monovalent metal Format: Write the name of the metal followed by the root of the nonmetal name followed by the suffix -ide Example: KCl

Nonmetal nameRoot of nonmetal name NitrogenNitr- OxygenOx- FluorineFluor- ChlorineChlor- BromineBrom- IodineIod- PhosphorusPhosph- SulfurSulf- SeleniumSelen-

Multivalent (also called type 2) metals Used to describe metals that can form more than one type of ion Includes all metals that are not monovalent These are atoms with electrons in the d sublevel. These electrons are quite mobile and move within the s,p, and d sublevels, resulting in a different number of valence electrons.

Multivalent metals The charge of a multivalent metal is represented by a Roman numeral written in parentheses, after the metal, in the name of the compound. I = +1 II = +2 III = +3 IV = +4

Writing Names Binary Ionic Compounds with multivalent metal Format: Write the name of the metal followed by the (Roman numeral that represents the charge of the metal) followed by the root of the nonmetal name followed by the suffix -ide *you will have to work backwards to determine the charge of the multivalent metal* Examples: FeBr 2

Ternary Used to describe compounds with more than 2 different elements Indicates that the compound contains a polyatomic ion.

Polyatomic ionsPolyatomic ions (7:07, Post) A group of covalently bonded atoms that acts as a single unit with a charge. *There is a list of common polyatomic ions on your reference materials.

Writing Names for Ternary Ionic Compounds with mono- or multivalent metals Format: metal (Roman numeral, if needed) negative polyatomic ion example: KOH or Format: positive polyatomic ion nonmetalide example: NH 4 Cl or Format: positive polyatomic ion negative polyatomic ion example: NH 4 OH

Naming Ionic Compounds Naming Ionic Compounds (10:44)

WRITING FORMULAS IONIC COMPOUNDS Option 1: Draw a Lewis dot diagram and use it to determine the correct ratio of metal to nonmetal atoms. Option 2: Write the chemical symbol for each element (metal, then nonmetal) with the oxidation number (charge of the ion) in the upper right corner of each symbol. Criss-cross the NUMBERS (not the + or -) to get the correct ratio. These numbers become the subscripts. If polyatomic ions are involved, enclose the symbols and subscripts in parentheses before criss-crossing. If necessary, reduce the subscript ratio. Watch ThisWatch This (9:32, Post) Watch ThisWatch This (4:58) WRITING FORMULAS FOR BINARY IONIC COMPOUNDS with type 1 metals WRITING FORMULAS FOR BINARY IONIC COMPOUNDS with type 1 metals (animation)

Formula Writing Practice: Write the formula for the compound that contains aluminum and sulfur. Write the formula for calcium fluoride. Write the formula for the iron (III) oxide. Write the formula for barium phosphate.

Covalent Molecules Many molecules have common names, such as: H2OH2O Common: Water CH 4 Common: methane NH 3 Common: Ammonia IUPAC: Nitrogen Trihydride

Naming Covalent Binary Molecules Add the correct prefix to each nonmetal. The least electronegative element goes first. For the second nonmetal, write the root of the name and add –ide. 1-mono 2-di 3-tri 4-tetra 5-penta 6-hexa 7-hepta 8-octa 9-nona 10-deca 19

Practice Write the name for N 2 O 5 Write the name for CCl 4 20

Writing formulas for molecules The prefixes tell you the subscript for each atom. No criss-cross. No reducing the subscript ratio. 21

Practice Write the formulas for carbon monoxide. Write the formula for disulfur pentoxide. 22

Percent Composition The percent by mass of an element in a compound is the mass of the element (in grams) divided by the mass of the compound (in grams), multiplied by 100 (to get a %). Watch ThisWatch This (3:26) Watch ThisWatch This (animation)

% Composition Practice What is the percent of Li and O in Li 2 O?

% Composition Practice What is the percent composition of Na 2 SO 3 ?

% Composition Practice How much sodium is in 25 grams of Na 2 SO 3 ?

Empirical formula Empirical - To be derived from observation, experiment, or data. Empirical formula - the simplest whole number ratio between two (or more) elements 29 Watch thisWatch this (animation) Watch this firstWatch this first (7:23 Bozeman)

Steps to determine the empirical formula of a compound: 1.Determine the mass of each element in the sample. 2.Divide the mass of each element by the molar mass (from the PT) to determine the number of moles of each element. Round to the thousandths (._ _ _ )! 3.Divide the # of moles of each element by the smallest # of moles. This is the mole ratio for each element in the compound. 4.If your answers to step 3 are whole numbers, these are written as the subscripts. 5.If your answers to step 3 are NOT whole numbers, multiply by 2, 3, or 5 to obtain a whole number if increments of 0.5, 0.3 or 0.2 are given, respectively. 30

31 Empirical formula practice: What is the empirical formula for a sulfur oxide compound containing 50% sulfur and 50% oxygen? Step 1: Since % means “parts per hundred”, assume we are working with a 100 g sample. That means we have 50 g of sulfur and 50 g of oxygen.

Step 2: Use dimensional analysis to convert grams to moles 50 g S __1 mol_ = moles S 32.1 g 50 g O _1 mol_ = moles O 16.0 g 32 Label Properly!! Round to thousandths (._ _ _)

Step 3: Divide by the smallest number of moles to obtain a mole ratio moles S = 1 S Label Properly!! moles O moles S = 2 O So, we have 1 S for every 2 O. These numbers become the subscripts and the formula is SO 2 In our example, we did not need the 4 th step since the ratio came out to a whole number. 33

A compound contains 54.1 g of Mg and 45.9 g of P. Determine the compound’s empirical formula. Note: This time, we already have the number of grams so we can skip to step 2. Empirical formula practice: 34

Step 2: Use Dimensional Analysis to convert grams to moles g Mg___1 mol_ = moles Mg 24.3 g 45.9 g P __1 mol_ = moles P 31.0 g 35 Label Properly!! Round to thousandths place (._ _ _ )

Step 3: Divide by the smallest number of moles to obtain a mole ratio moles P = 1 P Label Properly!! moles Mg moles P = 1.5 Mg Notice, the bottom answer did not come out to a whole number this time. 36

Skip to step 5 since answers are not whole numbers. Step 5: Multiply answers from step 3 so that you get whole numbers. We had 1.5 Mg and 1 P 0.5 = ½ flip it and you have your scale factor, x 2 = 3 Mg and 1 x 2 = 2 P. The ratio did not change, it is just a whole number ratio now. So, we have 3 Mg for every 2 P or the formula Mg 3 P 2 37

Now that you know the steps, here is a jingle to make them easier to remember: Percent to mass step 1 Mass to mole step 2 Divide by small step 3 Multiply ‘til whole steps 4 and 5 Note: You may not need all of the steps. 38

Molecular formula  A formula that is reducible.  It is a multiple of an empirical formula. Ex. C 8 H 12 is a molecular formula because the subscript ratio can be reduced.  C 8 H 12 is the molecular formula.  C 2 H 3 is the empirical formula. 39

Molecular formula Mass of molecular formula Empirical formula Mass of emprical formula This template can help you organize your information and find what you are missing. 40

Ex. The molar mass of a molecular formula is g/mole and it’s empirical formula is P 2 O 5. Determine the molecular formula.  Draw your chart and fill in the info from the problem. 41 ? g/mol P2O5P2O g/mol Now, divide the molar mass of the MF by the molar mass of the EF. ( g/mole)/( g/mole) = 2. Scale factor is 2. Multiply the subscripts in the EF by 2 and the MF is… P 4 O 10 from word problem use PT to calculate

Molecular formula practice A compound is made from 2.00 g carbon, g hydrogen, and 2.66 g oxygen. Its molar mass is 90.0 g/mole. Determine the molecular formula. 42