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Learn how to name and write formulas for ionic and covalent compounds, including examples and rules for naming polyatomic ions.
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Ionic Compounds: - are made up of positive and negative ions arranged in a crystal structure.(metal and non-metal)Covalent Molecules: - are made up of atoms sharing electrons.(non-metal and non-metal) 4.2 – Ionic and Covalent Compound Naming Salt, NaCl Water, H2O
Naming Ionic Compounds: • name of an ionic compound = positive ion negative ion-ide • Ex.1: magnesium and oxygen • positive ion negative ion-ide • Magnesium ox + ide • Magnesium oxide • Ex.2: what is the name of Ca3N2? • Ca = calcium; N = nitrogen • Drop the end of the negative ion and add –ide • Calcium nitride • Ex.3: What is the name of BaCl2? • Barium chloride Magnesium oxide is used as a drying agent.
Writing formulas for Ionic Compounds Remember: positive charges must = negative charges Ex.1: What is the formula for magnesium phosphide? • Magnesium is Mg2+ Phosphorous is P3– • Lowest common multiple of 2 and 3 is 6 • 3 Mg2+ ions & 2 P3– ions (6 +ve’s & 6 –ve’s) • Magnesium phosphide = Mg3P2 • Ex.2: What is the formula for calcium oxide? Calcium is Ca2+ Oxygen is O2– 1 Ca2+ ion & 1 O2– ion Calcium oxide = CaO
Drawing Formula Diagrams • More Examples: • Lithium nitride • Barium sulphide
Ionic Compound with a Multivalent Metal • Multivalent: some transition metals have more than one charge. • Roman numerals are used after the metal name to indicate which ion was used Ex. 1 What is the formula manganese(III) sulphide? • This manganese is Mn3+ Sulphur is S2– • Lowest common multiple of 3 and 2 is 6 • 2 Mn3+ ions and 3 S2– ions • Mn2S3
You try! What is the name for TiF4? • Titanium can be Ti4+ orTi3+ Fluorine is F– • From the ratio in the formula you can find out it is Ti4+ • 1 Ti4+ ion and 4 F– ions • Titanium (IV) fluoride
Polyatomic Ions • are made up of several atoms joined together by covalent bonds • The whole group has a + or – charge, not individual atoms. • Ex.1 What is the formula of sodium sulphate? Na+ and SO42– Na2SO4
Ex.2: What is the name of the compound KClO? K+ = potassium ClO– = hypochlorite Potassium hypochlorite Ex.3: What is the formula for Calcium nitrate? Ca2+ and NO3- Ca(NO3)2 * Note the brackets around NO3 show there are two of the nitrate ions present
Naming Simple Covalent Compounds • Prefixes are used before the atom name to indicate the number of atoms in the molecule. • Examples: CO = carbon monoxide CO2 = carbon dioxide • Write the most metallic atom (furthest left) first, then add -ide to the end of the second atom’s name
Examples: • What is the name of the molecule Si3P6? • Trisiliconhexaphosphide • What is the chemical formula for the molecule trinitrogen tetrachloride? • N3Cl4
How do you know which type it is? • To determine whether a compound is ionic or covalent: - Examine the formula • Ionic compounds start with a metal or the ammonium ion • Covalent compounds start with a non-metal Take the Section 4.2 Quiz