WHAT ARE IONIC COMPOUNDS • Ionic compounds are formed between elements that are in ionic form. • A simpler way of determining whether a compound is ionic is to see if there are any metals within the compound. • Ionic compounds are formed between metals and non-metals or between metals and polyatomic ions. 2
RULES FOR NAMING IONIC COMPOUNDS • For now we will focus only on the main group elements; transition metals are a bit tricky. • In order to form an ionic compound you must have a cation (usually a metal) + an anion (usually a nonmetal). • You always name the cation first, followed by the anion and replace the ending of the anion with “-ide”. 3
WHAT ELEMENTS BELONG TO THE MAIN GROUP??
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EXAMPLE • In order to name NaCl.
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MAIN GROUPS CHARGES • Elements found under the main group have set charges. • Charges represents how many electrons the element can lose or gain. • Notice how every metal has a positive charge and non-metals have negative charges. • Also, the charges are set for all elements belonging to a column. 6
CHARGES
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WRITING IONIC COMPOUNDS • In order to form a compound the overall charges of the compound must be zero. • Therefore, if you have a cation with a 3+ charge and an anion with a 2- charge, you will need 2 of the cation and 3 of the anion.
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EXAMPLE • To combine magnesium and nitrogen to form magnesium nitride you first have to look at their charges. • Mg2+ and N3-. The common factor between the two is 6, so you want to make the charges for each equal to 6.
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EXAMPLE
• Mg3N2; the small numbers indicates how many of each element are found in the compound. • By having 3 Mg you have 6+ charge. By having 2 N you have 6- charge. Together they have a netcharge of zero.
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PRACTICE PROBLEM • Name the following compounds: 1. MgO 2. Na2S 3. KF 4. Ca3P2 5. LiBr
PRACTICE PROBLEM • Write a compound with the following elements: 1. Oxygen and lithium 2. Strontium and nitrogen 3. Barium and chlorine
• Answers: 1. Li2O 2. Sr3N2 3. BaCl2
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NAMING IONIC COMPOUNDS WITH TRANSITION METALS • The rules for transition metals are almost the same as for regular metals. • However, unlike main-group metals, transition metals have multiple charges. • Therefore, when naming the compound you have to specify which charge the metal is carrying. • This is indicated by using roman numerals. 13
A FEW EXAMPLES
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HOW TO MAKE A COMPOUND WITH TRANSITION METALS • If you have chromium (II) and you want to make a compound using sulfur, you have to look at the charges for each ion and find a common multiple. • Chromium (II) has a 2+ charge and sulfur has a set charge of 2-.
• Therefore, you need one of each element to make a compound. The compound formula would be CrS. 15
PRACTICE PROBLEMS • Make a compound using the following elements: • Copper (I) and oxygen • Tin (II) and nitrogen • Lead (IV) and phosphorus • Gold (I) and iodine • Gold (III) and chlorine
• Answers: • • • • •
Cu2O Sn3N2 Pb3P4 AuI AuCl3
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COMPOUND TO NAMING
• When naming a compound that contains a transition metal in it you need to use roman numerals to indicate the charge of the cation. • In order to do so you have to refer to the anion to figure out what the charge of the cation is.
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EXAMPLE • If you are given the compound MnO and were asked to name it you would: • Look at the anion, which is the oxygen. You know that oxygen always has a charge of 2-. • Since there is only one oxygen, in order for the formula to have a balanced charge manganese has to carry a charge of 2+. • Therefore, the name of the compound is manganese (II) oxide.
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PRACTICE PROBLEMS • Name the following compounds: • • • • • •
CrP Co3N2 HgO FeS SnBr2 PbO2
• Answers: • Chromium (III) phosphide • Cobalt (II) nitride • Mercury (II) oxide • Iron (II) sulfide • Tin (II) bromide • Lead (IV) oxide
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NAMING IONIC COMPOUNDS WITH POLYATOMIC IONS
• Polyatomic ions are ions that contains more than one element in it. • It is very important to know your polyatomic ions and its charges.
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POLYATOMIC IONS
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NAMING IONIC COMPOUNDS WITH POLYATOMIC IONS • When naming compounds that contains polyatomic ions you name the cation as you normally would, and simply name the polyatomic element. • Example: MgSO4 will be named magnesium sulfate.
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NAMING IONIC COMPOUNDS WITH TRANSITION METALS AND POLYATOMIC IONS • When naming compounds that contains both a transition metal and a polyatomic ion you still have to use roman numerals for the metal, and the polyatomic ion will be named as is. • Example: Cu3(PO4)2 will be named copper (II) phosphate.
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PRACTICE PROBLEMS • Name the following compounds: • Sr(NO2)2 • AuSO3 • Al(CN)3