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Naming Ions
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What is a Monatomic Ion? A monotomic ion consists of a single atom with a positive or negative charge resulting from the loss or gain of valence electrons A cation is an ion with a positive charge. Metals in groups 1A, 2A, and 3A form a cation with the same charge as their group number The names of cations in these groups is the name of the element followed by ion or cation. Example: Na+ is sodium ion or sodium cation Ca2+ is calcium ion or calcium cation
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Naming Anions An anion is an atom that has gained electrons and thus has a negative charge The charge of a nonmetal anion in group A is determined by subtracting 8 from the group number. Elements in group 7A have a charge of -1 (7-8=-1) The name of an anion is not the same as the element’s name Anion names have the root of the element name with – ide added to it. Example: A chlorine ion is called chloride, and oxygen ion in called oxide
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Fluorine Ion Bromine Ion Selenium Ion Nitrogen Ion Fluoride Bromide
Practice Fluorine Ion Bromine Ion Selenium Ion Nitrogen Ion Fluoride Bromide Selenide Nitride
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Ions of Transition Metals
Transition metals do not form consitant charges when ioninzing like elements in the A group They can form multiple ions Iron can form Fe2+ and Fe3+ These cations are named differently than others. When naming an ion of a transition metal, write the name of the element folowed by it’s charge written in roman numerals following it. Example: Fe2+ is written as iron (II) and Fe3+ is written as iron (III)
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Exceptions Some transition metals have only one ionic charge.
The names of these elements do not have a roman numeral These excepetions include silver (Ag+), cadmium (Cd2+), and zinc (Zn2+)
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Pb2+ Pb4+ Cr2+ Cr3+ lead (II) lead (IV) chromium (II) chromium (III)
Practice Pb2+ Pb4+ Cr2+ Cr3+ lead (II) lead (IV) chromium (II) chromium (III)
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Polyatomic Ions A polyatomic ion is an ion composed of more than one atom. The names of most polyatomic ions in in –ite or –ate. All polyatomics ending in –ite or –ate contain oxygen
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1+ ammonium NH4+ 1- acetate C2H3O2- chlorate ClO3- hydroxide OH-
Charge Name Formula 1+ ammonium NH4+ 1- acetate C2H3O2- chlorate ClO3- hydroxide OH- cyanide CN- nitrate NO3- nitrite NO2- perchlorate ClO4- permanganate MnO4- 2- carbonate CO32- sulfate SO42- sulfite SO32- 3- phosphite PO33- phosphate PO43-
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Adding Hydrogen When the formula for a polyatomic ion contains hydrogen, it is a combination of an H+ ion and another polyatomic ion H+ + CO32- (carbonate) -> HCO3- hydrogen carbonate H+ + PO43- (phosphate) -> HPO42- hydrogen phosphate
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Naming Compounds with Polyatomic Ions
Naming a compound with a polyatomic ion works the same as with other ionic compounds Name the cation first then the anion Use the name of the polyatomic ion when naming.
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Example
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Naming and Writing Ionic Compounds
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What is a Binary Ionic Compound
A binary ionic compound is composed of two elements joined by an ionic bond. To name a binary ionic compound place the name of the cation first, followed by the name of the anion. The compound must remain neutral Example: NaBr would be sodium bromide Example: CuO would be copper (II) oxide This is known because the charge of oxygen is a 2-, so copper must have a charge of 2+ for the compound to be neutral
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Cu2O SnF2 SnS2 copper (I) oxide tin (II) fluoride tin (IV) fluoride
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Writing formulas for binary ionic compounds
If you know the name of a binary ionic compound, you can write it’s formula The net charge of the compound must be zero First figure out the charge of the atoms in the name of the compound Then use the charge of one compound as the subscript for the other compound Then reduce to the lowest whole number ratio
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Example Write the formula for calcium sulfide
From the periodic table, the charge of calcium is 2+ From the periodic table, the charge of sulfur is 6 -8 = -2 or S2- Ca2+ and S2- crossing the charges gives Ca2S2 Reducing to the lowest whole number ratio gives CaS
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Example Write the formula for iron (III) oxide
From the name of the ionic compound, the charge of iron is Fe3+ From the periodic table, the charge of oxygen is 6 -8 = -2 or O2- Fe3+ and O2- crossing the charges gives Fe2O3
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Practice copper (II) sulfide potassium nitride CuS K3N
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Compounds with Polyatomic Ions
Compounds with polyatomic ions behave the same as those without The method for writing their formula is the same as ordinary ionic compounds, except you look up the charge from a table of polyatomic ions instead of the periodic table
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Example Write the formula for calcium nitrate
From the periodic table, the charge of calcium is 2+ From the polyatomic table, the charge of nitrate is 1- Ca2+ and NO3- crossing the charges gives Ca(NO3)2 For a polyatomic ion, the subscript is written on the outside of the parenthesis
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