Ionic Compounds Positive Ion is called a CATION. They are metals. Negative Ion is called an ANION. They are non- metals.
4 Give the names of the following ions: Ba 2+ Al 3+ K + _________ __________ _________ N 3 O 2 F _________ __________ _________ P 3 S 2 Cl _________ __________ _________ Learning Check
Ionic Compounds Notice the cross over of Charges The Cation is always written FIRST, Anion Second. Ionic compounds are made up of metals and non- metals, the metal is written FIRST.
Formation of Ionic Compounds Crossing Rule Ca +2 + Cl -1 CaCl 2 But you MUST make sure to check to see if the whole number ratios can be REDUCED. If they can, you must reduce them.
Example of reducing: Cr 4+ O 2- If you just cross you get Cr 2 O 4 but this would NOT be the correct formula for chromium (IV) oxide. The correct formula is CrO 2
Naming Rules Step 1: The name of the metal is written first, the same way it is written on the periodic table Step 2: Write the name of non-metal second, BUT change the ending of the element to –ide. Step 3: Remember the crossing rule and remember to reduce!
9 Formula IonsName Cation Anion NaClNa + Cl – sodium chloride K 2 SK + S 2– potassium sulfide MgOMg 2+ O 2– magnesium oxide CaI 2 Ca 2+ I – calcium iodide Al 2 O 3 Al 3+ S 2– aluminum sulfide Examples of Ionic Compounds with Two Elements
Multiple Ionic Charges & Names Some Transition metals can have more than one charge and therefore more than one name. Element name Symbol Ionic Charges Roman numeral CopperCu +1, +2 I, II IronFe +2, +3 II, III LeadPb +2, +4 II, IV TinSn +2, +4 II, IV
How do I know if a metal is multi-valanced (mulitiple ionic charges)? Look at you table of ions!
12 Transition Metals Form Positive Ions Most transition metals and Group 4(14) metals, Form 2 or more positive ions Zn 2+, Ag +, and Cd 2+ form only one ion.
When writing the names Write the name of the element followed by the Roman numeral. EX: Cu 2+ is written Copper(II) So, what is the name of Fe 3+ ? How would you write the name of PbCl 4 ?
Metals with Variable Charge The names of transition metals with two or more positive ions (cations) use a Roman numeral after the name of the metal to identify ionic charge. 14
15 Examples of Names of Compounds with Variable Charge Metals
16 Naming FeCl 2 STEP 1 Determine the charge of the cation from the anion. Fe ion + 2 Cl – = Fe ion + 2– = 0 Fe ion = 2+ = Fe 2+ STEP 2 Name the cation by the element name, and use a Roman numeral to show its charge. Fe 2+ = iron(II) STEP 3 Write the anion with an ide ending. chloride STEP 4 Name the cation first, then the anion. iron(II) chloride
17 Naming Cr 2 O 3 STEP 1 Determine the charge of cation from the anion. 2Cr ions + 3O 2– = 2Cr ions + 3(2–) = 2Cr ions + 6– = 0 2Cr ions = 6+ Cr ion = 3+ = Cr 3+ STEP 2 Name the cation by the element name, and use a Roman numeral to show its charge. Cr 3+ = chromium(III) STEP 3 Write the anion with an ide ending. oxide STEP 4 Name the cation first, then the anion. chromium (III) oxide
Polyatomic Ionic Compounds What is a polyatomic ion? Polyatomic ions: groups of atoms that tend to stay together and carry an overall ionic charge. They still need two parts!
Table of Common Polyatomic Ions Name of polyatomic ion Ion fomula Ionic Charge Nitrate NO 3 - Hydroxide OH - Bicarbonate (hydrogen carbonate) HCO 3 - Chlorate ClO 3 - Carbonate CO 3 -2 -2 Sulfate SO 4 -2 -2 Phosphate PO 4 -3 -3 Ammonium NH 4 + +1
Polyatomic Compound Formulas Formulas for polyatomic compounds is determined the same way as ionic compounds. Cation first, Anion second, cross over rule But… brackets may be required!!! Al +3 + CO 3 -2 Al 2 (CO 3 )
Ammonium Ion The only positively charged polyatomic ion. NH 4 + ammonium ion Ammonium nitrate : ammonium ion NH 4 + nitrate ion NO 3 - NH 4 NO 3 Because this ion has a positive charge, it WILL come first.
Naming Polyatomic Compounds Step 1: Write the name of the metal first. Step 2: Write the name of the polyatomic ion second. NaH 2 CO 3 Sodium hydrogen carbonate or sodium bicarbonate NOT sodium hydrogen carbon oxide!!!!!!!
Hydrates A hydrate is a compound that has a specific number of water molecules within its solid structure. For example, in its normal state, copper(II) sulfate has five water molecules associated with it. Systematic name: copper(II) sulfate pentahydrate Formula: Cu(SO) 4 ∙ 5H 2 O Some other hydrates are BaCl 2 ∙ 2H 2 O LiCl ∙ H 2 O MgSO 4 ∙ 7H 2 O Sr(NO 3 ) 2 ∙ 4H 2 O
Hydrates When the water molecules are driven off by heating, the resulting compound, Cu(SO) 4, is sometimes called anhydrous copper(II) sulfate. Anhydrous means the compound no longer has water molecules associated with it.
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