Ionic Compounds

* Chemical Bond * Cation * Anion * Ionic Bond * Electrolyte * Formula Unit

* Forming Chemical Bonds

The force that holds two atoms together is a chemical bond. transfer electrons =ionic compounds share electrons =covalent compounds. Chemical Bonds In both cases, the bond forms because of an increase in stability.

* When an atom loses one or more of its valance electrons, it becomes a positive ion. * Example: Compare the valence electrons of Neon and Sodium. * Ne: 8 e- * Na: 1 e- * Na loses 1 e- its now a positive ion: +1 charge * This results in a positive sodium ion called a CATION.

* Group 1A: +1 ion. * Group 2A : +2 ion. * Group 3A : +3 ion. * Transition Metals: +2 ions and +3 ions.

* When an atom gains one or more of its valance electrons, it becomes a negative ion. * Example: Compare the valance electrons of Argon and Chlorine. * Ar: 8 * Cl: 7 * Cl gains 1 e- it’s a negative ion: -1 charge! * This results in a negative chlorine ion called a Anion!

* Group 5A : -3 ion. * Group 6A : -2 ion. * Group 7A : -1 ion. * Group 8A: stable * Group 4A can either gain 4 or lose 4 depending on the reaction. We will discuss in a later chapter.

* Get with your lab partners * Answer the following questions, to turn in! * One page per group

* What is a chemical bond? * Why do ions form? * What group of elements are unreactive and why? * Describe the formation of cations and anions. * Predict the change that must occur in the electron configuration if each of these atoms become stable… * Nitrogen * Sulfur * Barium * Lithium

* Obtain a sheet of paper * Draw a diagram of your element. Include: Protons, Neutrons, Electrons “in appropriate orbit”, Valance Electrons, Charge, Symbol, and Name. * Once you have completed that, illustrate how your element becomes an ion. * Dose it gain or lose electrons? * What noble gas does your element want to become? * If so, how many. If your element is a noble gas pick another element that isn’t taken.

* Formation and Nature of Ionic Bonds

* Ionic bond: an atom transfers its electrons to another atom. * Held together by the electrostatic (magnetic) attraction of the two ions.

* ionic compounds * brittle solids * high melting and boiling points * good conductors of heat and/or electricity. * dissolved in water its an electrolyte.

* Chapter 8.3 Names and Formulas for Ionic Compounds

* Names and Formulas for Ionic Compounds * A formula unit : simplest ratio of ions in an ionic compound. * We write ALL ionic compounds as formula units.

* ionic compounds = “electronically neutral” * + charge = - charge. * Example: Al and Cl * Al 3+ would need 3 Cl - ions. * Question: How many Fe 3+ and O 2- do you need to get electrically neutral? * ANSWER: 2 Fe 3+ AND 3 O 2-

* Monoatomic and Polyatomic Ions * Monoatomic ions : a single element. * Charge = oxidation number. * Example: Be 2+, Na +, Fe 3+, etc… * Polyatomic ions : more than one element. * combine together and have a net charge. * Example: SO 4 2-, NH 4 +, NO 2 -, C 2 H 3 O 2 -, etc…

 Golden Sheets

* Writing a Chemical Formula from the name * Example: Iron (III) Sulfate * Step 1: Fe SO 4 * Step 2: Fe 3+ SO 4 2- * Step 3: Total charge = +1 * Step 4: Fe 2 (SO 4 ) 3

* Writing a Chemical Formula from the name * Example: Barium Fluoride * Step 1: Ba F * Step 2: Ba 2+ F - * Step 3: Total charge = +1 * Step 4: BaF 2

* Naming Binary Ionic Compounds * Example: * NaCl: * FeO: * NH 4 Cl: * Sodium Chloride * Iron (II) Oxide * Ammonium Chloride

* Naming Binary Ionic Compounds * Step 1: cation first and anion second. * Step 2: Monoatomic cations use element name. * Step 3: Monoatomic anions use the ion name with the –ide ending. * Step 4: d-block cations write charge as a roman numeral in parentheses. * Step 5: a polyatomic ion, just use the name of the ion.

* Writing a Chemical Formula from the Name * Step 1: Write element symbol(s) for name of the ion(s). * Step 2: Write the charge of the ion(s). * Step 3: total charge = zero, you are done. total charge does not equal zero, change the subscripts so that the total charge equals zero (‘drop-n-cross’).

* End chapter 8