UNIT: Nomenclature Objectives: Lesson 1 of 3 You will learn which groups on the periodic table lose or gain electrons to become cations and anions You will learn what an ionic compound is and how they form You will learn how to write formulas for Ionic Compounds You will learn how to write the names of Ionic Compounds TOPIC: Ionic Compounds

Quickwrite In 1-2 sentences answer one of the questions below: What value will make the following expression correct: (???) = 0 What kind of charge will balance out a charge of -1? Consider the compound NaCl, How many Na atoms are present? How many Cl atoms or present?

Group Determines Charge Remember, groups of elements are in vertical columns and have similar chemical properties One of the reasons for this, is that the elements within the group form the same type of Ion For example, group 1 alkali metals like to lose a single electron and therefore always form +1 Cations Group 2 alkali earth metals always lose two electrons and therefore always from +2 Cations Group 13 elements like Aluminum lose three electrons and always form +3 Cations Group 16 elements like to gain two electrons and therefore always from -2 Anions Group 17 elements, the halogens, like to gain one electron and therefore always from -1 Anions

Group Determines Charge Elements in groups 3-12 have a hard time making up their mind These metals take on multiple positive charges For example, Consider Iron (Fe), Iron like to lose electrons to become either Fe +2 or Fe +3 cations Copper (Cu) can’t make up it’s mind either, it forms either Cu +1 or Cu +2 cations

What determines the charge of an ion? The group determines the charge of each ion Group 1 elements form +1 cations (Example: H +1, Na +1 ) Group 2 elements form +2 cations (Example: Mg +2, Ca +2 ) Group 13 elements form +3 cations (Example: Al +3 ) Group 16 elements form -2 anions (Example: O -2, S -2 ) Group 17 elements form -1 anions (Example: F -1, Cl -1 ) Elements in Groups 3-12 form cations with multiple charges (Example: Fe +2 or Fe +3, or Cu +1 or Cu +2 )

Use your notes or the periodic table below, determine the charge for the following ions: Na = Cl = O = Mg = Al = H = Na +1 Cl -1 O -2 Mg +2 Practice: Al +3 H Anions+1 Cations+2 Cations-2 Anions+3 Cations

Chlorine Atom Sodium Atom Bond +1 Ionic Compounds form between a cation and an anion Ionic Compounds form when a metal atom loses an electron(s) and transfers it to a nonmetal atom For example, consider the metal Sodium (Na) and the non-metal chlorine (Cl) When these two atoms bond to make a compound, the sodium loses one electron and transfers it to chlorine +1 Salt Grain or Cube Ionic Compounds Notice after losing an electron, sodium becomes a cation and chlorine becomes anion The result is a neutral Ionic Compound where the ionic charges are balanced out or neutral Table Salt or sodium chloride (NaCl) is a perfect example of an ionic compound Ionic Compound forms between a positive cations sand a negative anions

What is an Ionic Compound? A neutrally charged compound that contains a cation (positive ion) and anion (negative ion) Example: Sodium Chloride: Na +1 + Cl -1  NaCl Iron (III) oxide: Fe +3 + O -2  Fe 2 O 3

+1 Formula Units Salt Grain Cube Crystal Chlorine Anion Sodium Cation Bond +1 Ionic Compounds are always reduced down to their simplest ionic formula We call the simplest formula for an ionic compound a formula unit Lets revisit our table salt grain we saw earlier Ionic Compounds like sodium chloride (NaCl) are made up of a group or lattice of connected cations and anions Notice, each single sodium atom is bonded to a single chlorine atom This is the simplest ratio of atoms: 1 to 1 We could write the chemical formula as Na 2 Cl 2 BUT this wouldn’t represent the simplest unit in the ionic compound So instead we write NaCl to represent the simplest ratio of atoms -- 1 sodium atom/cation bonded to 1 chlorine atom/anion

What is a Formula Unit? The lowest ratio of atoms in an ionic compound Incorrect: Na 2 Cl 2 Correct: NaCl

Step #CationAnion 1. Charge 2. Number of atoms Overall Charge 3. Formula Na +1 Cl Determine the charge for the cation and anion For example, the Sodium atom/cation has a +1 charge and Chlorine atom/anion has a -1 charge 2. Add atoms/ions until the overall charge is neutral or zero Notice, the +1 charge of sodium is balanced by the -1 charge of chlorine creating an overall charge of zero 3. Once it is neutral, write the ionic formula, cation first and the anion second, use subscripts to show how many atoms make up the compound Now that it is neutral (+1-1= 0) we can write the formula NaCl as NaCl which tells us the compound is made up of one sodium atom and one chlorine atom Write the formula for the ionic compound Sodium Chloride; follow the steps below for help: -1 0 (neutral) +1 N NN Na Cl

Step #CationAnion 1. Charge 2. Number of atoms Overall Charge 3. Formula Ca +2 Cl Determine the charge for the cation and anion For example, the Calcium atom/cation has a +2 charge and Chlorine atom/anion has a -1 charge 2. Add atoms/ions until the overall charge is neutral or zero Notice, the +2 charge of Calcium is NOT balanced by the -1 charge of chlorine, therefore we need to another atom 3. Once it is neutral, write the ionic formula, cation first and the anion second, use subscripts to show how many atoms make up the compound Now that it is neutral ( = 0) we can write the formula CaCl 2 as CaCl 2 which tells us the compound is made up of one calcium atom and one chlorine atom Write the formula for the ionic compound Calcium Chloride; follow the steps below for help: -1 0 (neutral) +2 C CC Ca Cl Cl By adding another chlorine atom/anion, we will create a neutral charge ( = 0), completing step 2

Step #CationAnion 1. Charge 2. Number of atoms Overall Charge 3. Formula Fe +3 O Determine the charge for the cation and anion The roman numeral tells us the Iron atom/cation has a +3 charge and the Oxygen atom/anion has a -2 charge 2. Add atoms/ions until the overall charge is neutral or zero Notice, the +3 charge of Iron is NOT balanced by the -2 charge of Oxygen therefore we need to add more atoms 3. Once it is neutral, write the ionic formula, cation first and the anion second, use subscripts to show how many atoms make up the compound Now that it is neutral ( = 0), we can write the Fe 2 O 3 formula as Fe 2 O 3 which tells us the compound is made up of two Iron atoms and three Oxygen atoms Write the formula for the ionic compound Iron (III) Oxide; follow the steps below for help: -2 0 (neutral) +3 F FF Fe O OO O O -2 Fe By adding another Iron atom, & two more Oxygen atoms we will create a neutral charge ( = 0), completing step 2

What are the Steps for Writing Formulas for Ionic Compounds? 1. Determine the charge for each atom/ion 2. Add atoms/ions until their overall charge is neutral or equal to zero 3. Once it is neutral, write the ionic formula with the cation first and the anion second, use subscript numbers to show how many atoms make up the compound Step #CationAnion 1. Charge 2. Number of atoms Overall Charge 3. Formula Na +1 Cl Na Cl Cl 0 (neutral)

Practice: Write the chemical formula for the following Ionic Compounds: 1)Potassium Fluoride: 2)Calcium Oxide: 3)Magnesium Chloride: 4)Sodium Oxide: 5)Aluminum Oxide: 6)Copper (II) Chloride: 7)Copper (I) Chloride: KF Answer: K +1 + F -1  KF CaO Answer: Ca +2 + O -2  CaO MgCl 2 Answer: Mg +2 + Cl -1  MgCl 2 Na 2 O Answer: Na +1 + O -2  Na 2 O CuCl 2 Answer: Cu +2 + Cl -1  CuCl 2 CuCl Answer: Cu +1 + Cl -1  CuCl Al 2 O 3 Answer: Al +3 + O -2  Al 2 O 3

When naming ionic compounds there are certain steps you must use These steps will help you throughout this unit and the rest of the course: 1. The cation is always named first and the anion second For Example: for NaCl, we write Sodium Chloride 2. The cation takes it name from the name of the element For example: Na + is called sodium and Mg 2+ is called magnesium 3. The anion takes it’s name by taking the first part of the element name and adding -ide to the end For Example: The Cl - anion is called Chloride & the O 2- ion is called oxide 4. If the cation has more than one charge (it’s a transition metal) use roman numerals to indicate charge For Example: Iron can be either a Fe +2 or Fe +3 cation, so we write either Iron (II) or Iron(III) to indicate charge

1. The cation is always named first and the anion second 2. The cation takes it name from the name of the element 3. The anion takes it’s name by taking the first part of the element name and adding -ide to the end 4. If the cation has more than one charge (it’s a transition metal) use roman numerals to indicate charge

Practice: names Write the names for the following compounds below: 1)NaF 2)MgCl 2 3)CaS 4)Na 2 O 5)NiCl 2 6)CuO 7)Fe 2 O 3 Sodium Fluoride Answer: Sodium Fluoride Magnesium Chloride Answer: Magnesium Chloride Calcium Sulfide Answer: Calcium Sulfide Sodium Oxide Answer: Sodium Oxide : Nickel (II) Chloride Answer: Nickel (II) Chloride Copper (II) Oxide Answer: Copper (II) Oxide Iron (III) Oxide Answer: Iron (III) Oxide

Summarize: (you can always write you own) Explain in you own words how you were able to write chemical formulas for Ionic Compounds When writing Ionic Formulas, how do we deal with the complexity of multiple charges for Transition Metals? Explain why Na 2 Cl 2 is NOT the correct formula for sodium chloride: Do Ionic Compounds have a charge? Are they Neutral? Explain: When naming Ionic Compounds, what comes first? The metal or the Non-metal? What suffix do we put on the end of anions?