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) Salt, NaCl 4.2 – Ionic and Covalent Compound Naming Water, H 2 O

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 Ca 3 N 2 ? Ca = calcium; N = nitrogen Drop the end of the negative ion and add –ide Calcium nitride  Ex.3: What is the name of BaCl 2 ? 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 Mg 2+ Phosphorous is P 3–  Lowest common multiple of 2 and 3 is 6  3 Mg 2+ ions & 2 P 3– ions (6 +ve’s & 6 –ve’s)  Magnesium phosphide = Mg 3 P 2 Ex.2: What is the formula for calcium oxide? Calcium is Ca 2+ Oxygen is O 2– 1 Ca 2+ ion & 1 O 2– 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 Mn 3+ Sulphur is S 2– Lowest common multiple of 3 and 2 is 6 2 Mn 3+ ions and 3 S 2– ions Mn 2 S 3

You try! What is the name for TiF 4 ? Titanium can be Ti 4+ or Ti 3+ Fluorine is F – From the ratio in the formula you can find out it is Ti 4+ 1 Ti 4+ 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 SO 4 2– Na 2 SO 4

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? Ca 2+ and NO 3 - Ca(NO 3 ) 2 * Note the brackets around NO 3 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 CO 2 = 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 Si 3 P 6 ? TTrisilicon hexaphosphide WWhat is the chemical formula for the molecule trinitrogen tetrachloride? NN 3 Cl 4

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