Groundhog Day is Sunday!

Have fun watching the Super Bowl!

Thursday, Jan. 30 th : “A” Day Friday, Jan. 31 st : “B” Day Agenda  Collect lab: “Is it an Ionic Compound?”  ACT practice questions (Atomic Structure/Ion Energy)  Start Sec. 5.3: “Names/Formulas of Ionic Compounds”  In-Class/Homework: “What is an Oxidation Number?” “How are Chemical Compounds Named?” “Naming Ionic Compounds” Concept Review

Lab: “Is it an Ionic Compound?”  Make sure your table of contents is updated with this lab.  Don’t forget the reflection statement!  Put your lab folder back in the bin to be graded.

ACT Practice Questions  The science portion of the ACT is really a test of your critical thinking skills.  All the information you need to answer the questions should be provided in the passage, chart, graph, etc. that you are given.  Read through the sample passage and answer the questions.  YES, you do need to do this and YES, it WILL be graded!  When you’re finished, turn it in and pick up today’s notes…

Sec. 5.3: “Naming Ionic Compounds”  Salts that are made of a simple cation and a simple anion are known as binary ionic compounds.  The adjective binary means that the compound is made up of just two elements. Examples: NaCl Binary = MgO

Rules for Naming Simple Cations  Remember, metals LOSE electrons to form cations. (+ ions)  Simple cations take their names from the names of the elements. For example, K + is the potassium ion Ca 2+ is the calcium ion  What is the name of Li + ? lithium ion  What is the name of Sr 2+ ? strontium ion

Rules for Naming Simple Cations  When an element forms two or more stable ions (transition metals) the ion name includes roman numerals to show the charge. For example, copper can form either Cu + or Cu 2+ (see handout) Cu + = copper(I) ion Cu 2+ = copper(II) ion  This is read as “copper one ion” and “copper two ion”

Rules for Naming Simple Anions  Remember, non-metals GAIN electrons to form anions. (- ions)  The name of a simple anion is also taken from the name of the element, but the ending is changed to -ide. For example, Cl  is the chloride ion S 2- is the sulfide ion  What is the name of O 2- ? oxide ion  What is the name of N 3- ? nitride ion

“What is an Oxidation Number”  An oxidation number is simply the charge on the ion.  An oxidation number can be either positive (cation) or negative (anion).  What are the oxidation numbers of the following ions? Fe Cu + 1+

The Names of Ions Are Used to Name the Ionic Compound  Now that you know how to name the simple cations and anions, you can name the binary ionic compound.  The name of a binary ionic compound is made up of just two words: the name of the cation followed by the name of the anion. +

The Names of Ions Are Used to Name the Ionic Compound  Name the following ionic compounds: 1.NaCl sodium chloride 2.ZnS zinc sulfide 3.K 2 O potassium oxide 4.FeO (be careful!) iron (II) oxide 5.Mg 3 N 2 magnesium nitride

Writing Ionic Formulas  In an ionic compound, the positive charges of the cations need to equal the negative charges of the anions. (electrically neutral)  In sodium chloride, the sodium ion has a 1+ charge and the chloride ion has a 1- charge, so one Na + and one Cl - will add up to a total charge of zero. Na + Cl - NaCl  The formula for sodium chloride is written as NaCl to show this one-to-one ratio of ions.

Writing Ionic Formulas  In zinc sulfide, the zinc ion has a 2 + charge and the sulfide ion has a 2  charge, so one Zn 2+ and one S 2- will add up to a total charge of zero. Zn 2+ S 2- ZnS  The formula for zinc sulfide is written as ZnS to show this one-to-one ratio of ions.

Ionic Compounds Must Have no Overall Charge  In some ionic compounds, the charges on the cation and anion are different. For example, in magnesium nitride, the Mg 2+ ion has two positive charges, and the N 3− ion has three negative charges.  The cations and anions must be combined so that there are the same number of negative charges and positive charges. + = 0

Compounds Must Have no Overall Charge  In order for the overall charge to be zero, three Mg 2+ cations are needed for every two N 3  anions. Mg 2+ N 3- Mg 3 N 2  Subscripts are used to show the number of ions.

Example #1  Write the chemical formula for the ionic compound sodium nitride. Na + N 3- Na 3 N  Three Na + cations are needed to balance out the N 3- anion to make the overall charge of sodium nitride equal to zero.

Example #2  Write the chemical formula for the ionic compound aluminum oxide. Al 3+ O 2- Al 2 O 3  Two Al 3+ cations and three O 2- anions are needed to make the overall charge of aluminum oxide equal to zero.

Hints for writing ionic formulas 1.Find the charges on the cation and anion. 2.If the metal is a transition metal, look at the table to find the possible charges. When naming it, be sure to include a roman numeral in ( ) to indicate the charge on the cation. 3.Write the formula so that the charges balance out to zero.

Practice  Write the formulas for the following compounds: 1.Chromium (II) oxide CrO 2.Zinc bromide ZnBr 2 3.Sodium iodide NaI 4.Iron (III) oxide Fe 2 O 3 5.Aluminum bromide AlBr 3

In-Class/Homework 1.“What is an Oxidation Number” 2.“How are Chemical Compounds Named? 3.“Naming Ionic Compounds”  If you finish early, work on the concept review We will finish this section next time...