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Guide to Naming Ionic Compounds. February 18. Naming Ions and Ionic Compounds. Cations (+) The name of a cation is the same as the name of the element Find name either on the periodic table or from memory A few cations need Roman numerals with the name.
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Guide to Naming Ionic Compounds February 18
Naming Ions and Ionic Compounds • Cations (+) • The name of a cation is the same as the name of the element • Find name either on the periodic table or from memory • A few cations need Roman numerals with the name
Cations that need Roman Numerals • All d-block elements except Ag+, Zn2+, Cd2+ • Some p-block elements Zn2+ Ag+Cd2+
Roman Numerals • I, II, III, IV, V, VI, VII, IX, X, etc. • Some cations need Roman numerals because they can form more than one ion by losing different numbers of valence electrons • The numeral tells you the charge of the ion. For example: • Symbol Cation name • Ti2+ titanium (II) • Ti4+ titanium (IV)
Exceptions • All d-block elements need Roman numerals except Ag+, Zn2+, Cd2+ • Silver, zinc, and cadmium will only form one ion. The charge will always be the same for these three cations. • Symbol Cation name • Ag+ silver NOT: Silver (I) • Zn2+ zinc NOT: Zinc (II) • Cd2+ cadmium NOT: Cadmium (II)
Examples: Name to Symbol All cations have positive charges • Cation nameSymbol • Sodium Na+ • Hydrogen H+ • Vanadium (III) V3+ • Tin (II) Sn2+ We know the charge of the sodium and hydrogen cations by looking at a periodic table The Roman numeral tells us the charge of the vanadium and tin ions
Note on Determining the Charge • Depends on number of valence electrons • How many electrons does the atom need to gain or loose to reach a full valence shell? • Will loose to reach 0 electrons or • Will gain to reach 8 electrons • If it looses electrons, the ion is positive • If it gains electrons, the ion is negative
Examples: Symbol to Name Sr2+ and K+ do not need Roman numerals because they are in the s-block • Symbol Cation name • Sr2+ Strontium • Cd2+ Cadmium • Cu2+ Copper (II) • Pb3+ Lead (III) • Pb2+ Lead (II) • K+ Potassium Cadmium does not need a Roman numeral because it is one of the three d-block exceptions The charge of the ion symbol tells us what Roman numeral to write in the name. Copper and lead need Roman numerals because they are found in the d-block and lower-left p-block and form more than one ion.
Naming Ions and Ionic Compounds • Anions (-) • The name of a anion is similar to the name of the element • Find name either the periodic table or from memory • Drop the ending of the element name • Add –ide to the stem • NOTE: If the anion’s name ends in –ide and is NOT cyanide (CN-), hydroxide (OH-), or peroxide (O22-), it will be an ion of an element you find on the periodic table
Examples: Name to Symbol All anions have negative charges • Cation nameSymbol • Bromide Br- • Oxide O2- • Nitride N3- • All the names end in –ide: • Bromine bromide • Oxygen Oxide • Nitrogen Nitride We know the charge of the anions by looking at a periodic table
Examples: Symbol to Name • Symbol Element nameAnion name • S2-sulfur Sulfide • Cl-chlorine Chloride • P3-phosphorous Phosphide
Polyatomic Ions • A molecule with a charge • You will need to memorize the names • They behave just like monotomiccations and anions
Examples: Name to Formula • Ion nameFormula • Oxalate C2O42- • Chlorate ClO3- • Acetate CH3COO- • Ammonium NH4+
Examples: Formula to Name • Ion nameFormula • O22- Peroxide • CH3COO- Acetate • Cr2O72- Dichromate • AsO43- Arsenate • MnO4- Permanganate
Helpful Tip 1: Hints in names • Look for clues in the polyatomic ion names • Example: • Cr2O72-Dichromate • Chromate sounds like chromium • Di means two • Dichromate has two chromiums in it
Helpful Tip 2: -ate vs. –ite • If two similar ions have names that end in –ate and –ite, -ate will have more oxygen • ClO3- Chlorate3oxygens • ClO2- Chlorite2oxygens • NO3- Nitrate3oxygens • NO2- Nitrite2oxygens • SO42-Sulfate4oxygens • SO32- Sulfite3oxygens
Helpful Tip 3: Per- and Hypo- • Per-: 1 more oxygen, same charge • Hypo-: 1 less oxygen, same charge • ClO4- Perchlorate 4 oxygens • ClO3- Chlorate3oxygens • ClO2- Chlorite2oxygens • ClO- Hypochlorite 1 oxygen