Ionic compounds Ionic compounds are: 1. Made up of oppositely charged ions held together strongly in well- organized units. 2. Hard solids at room temperature and are difficult to melt. Look at the structure of magnesium oxide.
The smallest part of compounds Molecule: the smallest unit of the compound in a covalent compound. Formula unit The simplest ratio of ions in a compound.
Binary Ionic Compounds You will learn how to name and write formulas for ionic compounds. Binary compound: a compound that contains only two elements. Ex: Sodium chloride (NaCl), potassium iodide (KI) and (CaF2) calcium florid (contain more than one ion of each element)
Predicting Charge on Ions
Oxidation numbers for elements in Groups 3 through 12, the transition elements, cannot be predicted by group number. Aluminum is in Group 13, so it loses its three outer electrons to become an Al 3+ ion; oxygen is in Group 16 and has six valence electrons, so it gains two electrons to become an O 2– ion.
How to name a binary ionic compound To name a binary ionic compound, first write the name of the positively charged ion, usually a metal, and then add the name of the nonmetal or negatively charged ion, whose name has been modified to end in -ide. Magnesium combines with oxygen to form a compound called magnesium oxide (MgO).
How to write the formula Sodium chloride contains sodium ions that have a 1+ charge and chloride ions that have a 1– charge. the sum of the charges in an ionic compound must always equal zero.
Learning Check Write the correct formula for the compounds containing the following ions: A. Na +, S 2- 1) NaS 2) Na 2 S3) NaS 2 B. Al 3+, Cl - 1) AlCl 3 2) AlCl 3) Al 3 Cl C. Mg 2+, N 3- 1) MgN 2) Mg 2 N 3 3) Mg 3 N 2
Solution A. Na +, S 2- 2) Na 2 S B. Al 3+, Cl - 1) AlCl 3 C. Mg 2+, N 3- 3) Mg 3 N 2
Naming Binary Ionic Compounds Contain 2 different elements Name the metal first, then the nonmetal as - ide. Examples: NaClsodium chloride ZnI 2 zinc iodide Al 2 O 3 aluminum oxide
Learning Check Complete the names of the following binary compounds: Na 3 Nsodium ________________ KBrpotassium________________ Al 2 O 3 aluminum ________________ MgS_________________________
Solution Complete the names of the following binary compounds: Na 3 Nsodium nitride KBrpotassium bromide Al 2 O 3 aluminum oxide MgSmagnesium sulfide
Learning Check A. The formula for the ionic compound of Na + and O 2- is 1) NaO2) Na 2 O3) NaO 2 B. The formula of a compound of aluminum and chlorine is 1) Al 3 Cl2) AlCl 2 3) AlCl 3 C. The formula of Fe 3+ and O 2- is 1) Fe 3 O 2 2) FeO 3 3) Fe 2 O 3
Solution A. The formula for the ionic compound of Na + and O 2- is 2) Na 2 O B. The formula of a compound of aluminum and chlorine is 3) AlCl 3 C. The formula of Fe 3+ and O 2- is 3) Fe 2 O 3
Transition Metals Transition Metals Many form 2 or more positive ions or or 3+ Ag + Cd 2+ Cu +, Cu 2+ Fe 2+, Fe 3+ silver cadmium copper(I) ion iron(II) ion ion copper (II) ion iron(III) ion Zn 2+ zinc ion
Names of Variable Ions Use a roman number after the name of a metal that forms two or more ions Transition metals and the metals in groups 4A and 5A FeCl 3 (Fe 3+ ) iron (III) chloride CuCl (Cu + ) copper (I) chloride SnF 4 (Sn 4+ ) tin (IV) fluoride PbCl 2 (Pb 2+ )lead (II) chloride Fe 2 S 3 (Fe 3+ )iron (III) sulfide
Learning Check Complete the names of the following binary compounds with variable metal ions: FeBr 2 iron (_____) bromide Cu 2 Ocopper (_____) oxide SnCl 4 ___(_____ ) ______________ Fe 2 O 3 ________________________ CuS________________________
Solution Complete the names of the following binary compounds with variable metal ions: FeBr 2 iron ( II ) bromide Cu 2 Ocopper ( I ) oxide SnCl 4 tin (IV) chloride Fe 2 O 3 iron (III) oxide CuScopper (II) sulfide
Learning Check Name the following compounds: A. CaO 1) calcium oxide2) calcium(I) oxide 3) calcium (II) oxide B. SnCl 4 1) tin tetrachloride2) tin(II) chloride 3) tin(IV) chloride C. Co 2 O 3 1) cobalt oxide 2) cobalt (III) oxide 3) cobalt trioxide
Solution Name the following compounds: A. CaO1) calcium oxide B. SnCl 4 3) tin(IV) chloride C.Co 2 O 3 2) cobalt (III) oxide
Compounds Containing Polyatomic Ions Polyatomic ion: An ion that has two or more different elements.
Compounds Containing Polyatomic Ions
Ionic compounds may contain: 1. positive metal ions bonded to negative polyatomic ions, such as in NaOH. 2. negative nonmetal ions bonded to positive polyatomic ions, such as in NH 4 I. 3. or positive polyatomic ions bonded to negative polyatomic ions, such as in NH 4 NO 3.
How to write formula of Compounds Containing Polyatomic Ions Remember that the sum of the positive and negative charges must equal zero. Write a subscript outside the parentheses to show the number of polyatomic ions in the compound. The formula for the compound that contains one magnesium ion and two nitrate ions is Mg (NO 3 ) 2.
How to name a compound containing a polyatomic ion To name a compound containing a polyatomic ion, follow the same rules as used in naming binary compounds. The name of the compound composed of calcium and the carbonate ion is calcium carbonate. To form a neutral compound, one Ca 2+ ion must combine with one CO 3 2– ion to give the formula CaCO 3.
Hydrates Hydrate: A compound in which there is a specific ratio of water to ionic compound. For example CaSO4 2H 2 O is calcium sulfate dihydrate. Hygroscopic: compounds can easily become hydrates by absorbing water molecules from water vapor in the air. Example is Sodium Carbonate (Na 2 CO 3 ).
Hydrates Deliquescent: Substances those are so hygroscopic that they take up enough water from the air to dissolve completely and form a liquid solution.
Hydrates The dot in the formula represents a ratio of compound formula units to water molecules. For example, CaSO 4 2H 2 0 is the formula for a hydrate of calcium sulfate that contains two molecules of water for each formula unit of calcium sulfate.
How To name hydrates To name hydrates, follow the regular name for the compound with the word hydrate, to which a prefix has been added to indicate the number of water molecules present. The name of the compound with the formula CaSO4 2H2O is calcium sulfate dihydrate.
Anhydrous compound Heating hydrates can drive off the water. This results in the formation of an anhydrous compound—one in which all of the water has been removed. In some cases, an anhydrous compound may have different color from that of its hydrate. For example: CuSO 4.5H 2 O is (blue) while anhydrous of CuSO 4 is (white)