In This Lesson: Unit 3: Ionic and Molecular Compounds Ionic Nomenclature and Polyatomic Ions (Lesson 1 of 4) Today is Wednesday, October 11 th, 2017 Pre-Class: Can you name these compounds? H 2 O CO 2 NaCl HCl Stuff You Need: Periodic Table Today you will need your periodic tables that show the charges for transition metals.
Pre-Class Deux Can you name these compounds? O 2 Oxygen gas O 3 Ozone gas CO Carbon monoxide H 2 SO 4 Sulfuric acid
Today s Agenda Namin stuff. In today s case, ionic compounds and polyatomic ions. Where is this in my book? P. 264 and following
By the end of this lesson You should be able to name ionic compounds, including those with polyatomic ions.
Quick Reminders A compound is a chemical combination of two or more elements (like the pre-class ones). Subscripts indicate how many atoms of an element are present. H 2 O = 2 Hydrogen, 1 Oxygen CO 2 = 1 Carbon, 2 Oxygen Note that subscripts only apply to the letter next to them (unless there are parentheses).
Quick Reminders Chemists don t write ones. Na + has a charge of 1+. Cl - has a charge of 1-. K 2 S has one sulfur atom.
Quick Reminders Charge (1-) Nd 2 - Subscript (2 Nd atoms)
Quick Reminders For elements whose symbols have two letters (or even three), only the first letter is capitalized. For example, Cobalt is abbreviated Co. If you write CO, another person might think it s a compound of Carbon (C) and Oxygen (O). That s carbon monoxide! Both are deadly, but don t confuse them.
Quick Reminders Remember that cations are positively-charged ions, and anions are negatively-charged. Most cations are metals; some polyatomic ions. Example: Ca 2+, NH 4 + Most anions are nonmetals; many polyatomic ions. Example: Cl -, SO 4 2-
Cations and Anions And since cations and anions attract one another they form ionic bonds, making ionic compounds.
Need to Know Information Now, to name any compound or derive its formula, you need to know: What kind of elements are involved? Metal, nonmetal, or metalloid. How many elements are there? 2 binary compound 3 ternary compound (usually has a polyatomic ion) Are there polyatomic ions?
Wait polyatomic? Polyatomic ions are (usually) small compounds that behave as one ion. In other words, there s more than one element, but they act as one. Poly-atomic get it? You should memorize as many of these as possible. Yes, really. Here s a hint: Anything ending in -ide, except Hydroxide, Peroxide, and Cyanide, will be found on the periodic table. Everything else is on the polyatomic ion charts.
Polyatomic Ion List I will give you a list of polyatomic ions, but I assure you that studying/memorizing the list will be extremely helpful. Note: You will not have a polyatomic ion list on the final. Also helpful will be the following slide that shows how many of the names for polyatomic ions are determined. Important Note: Hydrogen carbonate is the same as Bicarbonate. Hydrogen sulfite is the same as Bisulfite. Hydrogen sulfate is the same as Bisulfate. Acetate is more commonly written as C 2 H 3 O 2-, but there are two ways to write it. See?
Most Common Polyatomic Ions These are worth memorizin! Acetate (C 2 H 3 O 2- ) Carbonate (CO 3 2- ) Chlorate (ClO 3- ) Hydroxide (OH - ) Nitrate (NO 3- ) Phosphate (PO 4 3- ) Sulfate (SO 4 2- ) Ammonium (NH 4+ )
Naming Polyatomic Ions There s a system to how these polyatomic ions are named. It s not the most helpful, but getting a little familiar with this might be useful. Let s take a look
Naming Polyatomic Ions Main Ion ClO 3 - Chlorate CO 3 2- Carbonate PO 4 3- Phosphate NO 3 - Nitrate SO 4 2- Sulfate BrO 3 - Bromate
Naming Polyatomic Ions with Chlorine Anion Name Number of Oxygen Atoms Cl - Chloride 0 ide ClO - ClO - 2 ClO - 3 ClO - 4 Hypochlorite Chlorite Chlorate Perchlorate 1 hypo ite (2 fewer than main) 2 ite (1 fewer than main) 3 ate (main ion) 4 per ate (1 more than main)
Naming Polyatomic Ions No O -2 O -1 O Main Ion +1 O Cl - Chloride ClO - Hypochlorite ClO 2 - Chlorite ClO 3 Chlorate ClO 4 - Perchlorate STAR WARS! (not real) CO 3 2- Carbonate P 3- Phosphide PO 3 3- Phosphite PO 4 3- Phosphate N 3- Nitride N 2 O 2 2- Hyponitrite NO 2 - Nitrite NO 3 - Nitrate S 2- Sulfide SO 3 2- Sulfite SO 4 2- Sulfate Br - Bromide BrO - Hypobromite BrO 2 - Bromite BrO 3 - Bromate BrO 4 - Perbromate
Time for some practice! Polyatomic Ion Puzzle The puzzle is like dominoes - match the names of polyatomic ions to their formulas. Note that some sides may not be used. Some ions are represented more than once. Try many possibilities don t give up! HINTS: There are four obvious corner pieces (but no edges). Cyanide, chromate, dichromate, hydrogen carbonate, and permanganate only have one match each. It s a 4x4 grid.
Now that that s over Let s make sure we know how to predict ionic charges a little more specifically.
Group 1 Group 1: Lose 1 electron to form 1+ ions H + Li + Na + K +
Group 2 Group 2: Lose 2 electrons to form 2+ ions Be 2+ Mg 2+ Ca 2+ Sr 2+ Ba 2+
Ga 3+ Group 13 Al 3+ B 3+ Group 13: Group 13: Lose 3 electrons to form 3+ ions
Group 14 Group 14: Group 14: Rarely form ions
Group 14 Group 14: Ge 4+ Sn 4+ Pb 2+ Group 14: 4+ or 2+ ions
Group 15 N 3- P 3- As 3- Nitride Group 15: Gain 3 electrons to form 3- ions Phosphide Arsenide
O 2- S 2- Se 2- Oxide Sulfide Selenide Group 16 Group 16: Group 16: Gain 2 electrons to form 2- ions
I - Br - F - Cl - Iodide Bromide Fluoride Chloride Group 17 Group 17: Group 17: Gain 1 electron to form 1- ions
Group 18 Group 18: Group 18: Noble gases do not form ions
Hey, wait a sec By now you may be thinking, But Mr. G didn t you forget the transition metals? No. I did not. Chill. They re just weird.
Groups 3-12: Transition Metals Transition Metals: Many transition metals have more than one oxidation state Fe 2+ = Iron (II) Fe 3+ = Iron (III)
Multivalent Elements For transition elements (and some others), things can get tricky. Most have either 1 or 2 valence electrons. Some have more or less. Some have more than one amount of valence electrons. These are called multivalent metals because they have multiple valence numbers (charges). They are often written as this: Element (charge written as Roman numeral)
Common Multivalent Elements Copper (Cu) either 1 or 2 valence electrons. Copper (I) or Copper (II) 1 + or 2 + Nickel (Ni) either 2 or 3 valence electrons. Nickel (II) or Nickel (III) 2 + or 3 + Iron (Fe) either 2 or 3 valence electrons. Iron (II) or Iron (III) 2 + or 3 + Lead (Pb) either 2 or 4 valence electrons. Lead (II) or Lead (IV) 2 + or 4 + Tin (Sn) either 2 or 4 valence electrons. Tin (II) or Tin (IV) 2 + or 4 + Mercury (Hg) either 1 or 2 valence electrons. Mercury (I) or Mercury (II) 1 + or 2 +
However Some transition elements have only one possible oxidation state. Zinc (Zn) Zn 2+ Silver (Ag) Ag +
Valence Electrons and Multivalent Metals How many valence electrons does Iron (I) have? One. If it forms a +1 charge, it must have one electron to give up. How many valence electrons does Lead (IV) have? Four. If it forms a +4 charge, it must have four electrons to give up.
One weird exception You will see this come up every once in a while in this class but it won t be something you need to know for a test. It s called the Mercury (I) ion. Mercury (I) sounds like it should be Hg + but it s actually Hg 2 2+. Compounds with that weird complex ion are known as mercurous compounds.
Nomenclature Before we begin nomenclature, I m going to hand out a flowchart to everyone. Treat this piece of paper like it s a piece of solid Au, or Pt. Get it? Anyway, this paper will save you a lot of frustration. Trust me.
Nomenclature We now reach something called nomenclature, which is a fancy name for a very particular naming system. Ain t that a coincidence?
Nomenclature When naming ionic compounds (that s today s lesson), cations names are not changed. In other words, a sodium ion is called a sodium ion. Anions, however, are referred to by the element stem followed by ide. Chlorine becomes chloride, nitrogen becomes nitride, fluorine becomes fluoride (becomes toothpaste). Thus, NaCl is called sodium chloride, not sodium chlorine or sodide chloride or whatever.
Procedure To name ionic compounds, follow these four steps: 1. Write the symbols for the cation and anion, including charges. Put polyatomic ions in a circle. Do not change anything in the circle. 2. Check to see if the charges are balanced (=0). 3. Balance charges, if necessary, using subscripts. 4. If you need more than one of a polyatomic ion, use parentheses at the end. ONLY for polyatomics! Simplify subscripts, remove circles and charges to clean it all up.
Remember the Goal Your goal is to make sure that the positive parts of the compound are completely balanced with the negative ones. In other words, the overall charge adds to 0.
Quick Reminder Charge (1-) Nd 2 - Subscript (2 Nd atoms)
Example: Iron (III) chloride 1. Write the symbols for the cation and anion, including charges. 2. Check to see if the charges are balanced (=0). 3. Balance charges, if necessary, using subscripts. Clean it up (and don t leave a space). Fe 3+ Cl - 3 Total Positive Charge 3+ Not balanced! Total Negative Charge 1-3-
Example: Barium nitrate 1. Write the symbols for the cation and anion, including charges. Put polyatomic ions in a circle. 2. Check to see if the charges are balanced (=0). 3. Balance charges, if necessary, using subscripts. 4. If you need more than one of a polyatomic ion, use parentheses. ONLY for polyatomics! Clean it up. Ba 2+ ( NO - 3 ) 2 Total Positive Charge 2+ Not balanced! Total Negative Charge 1-2-
About Parentheses Parentheses make a difference only when you have multiple polyatomic ions. Imagine if you need multiple pairs of shoes. You want two sets of shoes, not just two left shoes. Similarly, (OH) 2 says you want two sets of OH. However, OH 2 says you want water and wrote it backward. Parentheses don t make a difference if it s just an atom or one polyatomic ion. You write Cl 2, not (Cl) 2. (NO 3 ) 3 or (OH) 2 are not the same as N 3 O 9 and OH 2.
Example: Ammonium sulfate 1. Write the symbols for the cation and anion, including charges. Put polyatomic ions in a circle. 2. Check to see if the charges are balanced (=0). 3. Balance charges, if necessary, using subscripts. 4. If you need more than one of a polyatomic ion, use parentheses. ONLY for polyatomics! Clean it up. ( NH4 + ) SO 2-4 2 Total Positive Charge 2+ 1+ Not balanced! Total Negative Charge 2-
Example: Aluminum sulfide 1. Write the symbols for the cation and anion, including charges. 2. Check to see if the charges are balanced (=0). 3. Balance charges, if necessary, using subscripts. Clean it up. Al 3+ S 2-2 3 Total Positive Charge 6+ 3+ Not balanced! Total Negative Charge 6-2-
Alternative Method: The Cross-Over Al 3+ S 2-2 3
Cross-Over Weaknesses Beware! Try doing calcium sulfide using the cross-over method. Wrong: Ca 2 S 2 Right: CaS Reason? The charges were already balanced. Try doing germanium oxide using the crossover method. Wrong: Ge 2 O 4 Right: GeO 2 Reason? Always simplify the subscripts if possible.
Example: Magnesium carbonate 1. Write the symbols for the cation and anion, including charges. Put polyatomic ions in a circle. 2. Check to see if the charges are balanced (=0). Clean it up. Remember to simplify. Mg 2+ CO 3 2- Total Positive Charge 2+ Are balanced! Total Negative Charge 2-
Example: Zinc hydroxide 1. Write the symbols for the cation and anion, including charges. Put polyatomic ions in a circle. 2. Check to see if the charges are balanced (=0). 3. Balance charges, if necessary, using subscripts. 4. If you need more than one of a polyatomic ion, use parentheses. ONLY for polyatomics! Clean it up. Zn 2+ ( OH - ) 2 Total Positive Charge 2+ Not balanced! Total Negative Charge 1-2-
Example: Aluminum phosphate 1. Write the symbols for the cation and anion, including charges. Put polyatomic ions in a circle. 2. Check to see if the charges are balanced (=0). Clean it up. Al 3+ PO 4 3- Total Positive Charge 3+ Are balanced! Total Negative Charge 3-
Practice To practice all this stuff, let s turn to the Nomenclature Practice Sheet worksheet, first page (side with the hole punches on the left). Try the first section (1-12).
Now let s do all that again. Backwards. You ve now learned how to write the formula of an ionic compound from its name. Now let s take the formula of an ionic compound and write its name.
Binary Compounds Binary compounds are those with two elements. Example: CaCl 2 For these, first write the cation: Calcium Then write the anion root (chlor ) with the suffix ide. chloride Calcium chloride! Key: The cation always goes first.
Binary Compounds What s the name of NaCl? Sodium chloride Al 2 O 3 Aluminum oxide AlN Aluminum nitride
Binary Compounds What s the name of MgI 2? Magnesium iodide AlCl 3 Aluminum chloride Na 3 P Sodium phosphide
Binary Compounds Remember there are some elements that are multivalent. For these, you need to specify which charge that particular ion is carrying (in parentheses). Do this by figuring out the negative charge and working backward to find the cation charge. Example on the next slide
Binary Compounds with Multivalent Elements What is the name of PbCl 2? Well, we know it s Lead ( ) chloride, but we need to figure out the kind of lead we have. Lead could be 4+, 2+, or possibly something else. To figure that out, let s start with Chlorine. Two chlorines each show up to this party, each with a 1- charge. Total charge? 2-. With one Lead atom balancing this out, the Lead must be Lead (II). Lead (II) chloride!
Binary Compounds with Multivalent Elements What s the name of PbO 2? Lead (IV) oxide Mn 2 O 3 Manganese (III) oxide CuCl 2 Copper (II) chloride Ti(Cr 2 O 7 ) 2 Titanium (IV) dichromate +4 +4-4 PbO 2 +6-6 Mn 2 O 3 +2-2 CuCl 2-4 Ti(Cr 2 O 7 ) 2
Ternary Compounds Some compounds, like that last one, contain more than two elements. Ternary compounds contain three. They often include polyatomic ions. Naming works the same way. The trick is to know when you re looking at a polyatomic ion. How do you know? There will be a total of more than two elements there!
Ternary Compounds NaNO 3 Sodium nitrate Fe 2 (SO 4 ) 3 Iron (III) sulfate Cesium perchlorate CsClO 4 Ammonium phosphate (NH 4 ) 3 PO 4 Calcium hydroxide Ca(OH) 2
Practice To practice all this stuff, let s turn to the Nomenclature Practice Sheet worksheet, first page. Try the second section (13-24).
Takeaways Roman numerals tell you the charge of an atom, NOT how many there are. Subscripts tell you how many atoms there are. Roman numerals are used only for cations that make multiple charges. Also, they are only used in names, not formulas. Parentheses are used only when you need more than one of a polyatomic ion. Never around a single element.
It s time to play Fix That Ionic Compound! I ll give you a name and a formula. Your job is to fix the part that is in bold text.
Fix That Ionic Compound! Potassium sulfide is K 2 S 1 K 2 S BaI 2 is barium iodine Barium iodide SrBr 2 is strontium (II) bromide Strontium bromide Titanium (IV) oxide is Ti(IV)O 2 TiO 2 Corrections
Fix That Ionic Compound! CuCl 2 is copper chloride Copper (II) chloride The lead in PbO 2 has a charge of 2+ 4+ Corrections Magnesium oxide is Mg 2 O 2 MgO Sodium nitrate is Na 3 N NaNO 3
Fix That Ionic Compound! There are 4 phosphate molecules in AlPO 4 1 Ca(CN) 2 is calcium carbon nitride Calcium cyanide Corrections Strontium hydroxide is SrOH 2 Sr(OH) 2 Ammonium chlorite is NH 4 (ClO 2 ) NH 4 ClO 2
Closure Remind me what the name of this ion is: Cl - Chloride And do you know what HCl is? Hydrochloric Acid Remind me what polyatomic ion this is: SO 4 2- Sulfate And do you know what H 2 SO 4 is? Sulfuric acid Any pattern here?
Closure Part Deux What s the name of this compound? CO 2 Carbon dioxide And what s the name of this compound? CO Hint: It s toxic but odorless and colorless. Double Hint: You probably own a detector for it. Triple Hint: It s not smoke. Carbon monoxide. What s up with that? Why isn t it carbon oxide? Hint: Location on the table? Double Hint: Metal or nonmetal?
Extra Practice For extra practice, turn your Nomenclature Practice Sheet worksheets face down and try #1-20.