Formulas for Ionic Compounds

Formulas for Ionic Compounds

Ionic compounds are made up of a METAL and a NONMETAL and are generally referred to as SALTS.

Writing a Formula Problem: Write the formula for the ionic compound that will form between sodium and chlorine. Write the symbol for sodium first (because it s the metal) along with its combining capacity. Then write the symbol for chlorine with its combining capacity. Na + Cl How do you know which is the metal? It has a positive cc, and it s further left on the periodic table

The goal is to balance the positive and negative charges to make a neutral compound Na + Cl - are the charges balanced? YES! So the formula is NaCl

What is the ionic formula for a compound of barium and bromine? Ba +2 Br - We need another Br to balance the charges! Br - Thus, the formula is BaBr 2

Write the formula for lithium with oxygen. Write the formula for magnesium with oxygen. Li + O -2 Li + = Li 2 O Mg +2 O -2 = MgO

Learning Check Write the correct formula for the compounds containing the following ions: A. Na +, S 2-1) NaS 2) Na 2 S 3) 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

Naming Binary Ionic Compounds Contain 2 different elements Name the metal first with its regular name, then the nonmetal as ide ending. Examples: 1) NaCl 1) sodium chloride 2) ZnI 2 2) zinc iodide 3) Al 2 O 3 3) aluminum oxide

Learning Check Complete the names of the following binary compounds: Na 3 N sodium KBr potassium Al 2 O 3 MgS aluminum

Solution Complete the names of the following binary compounds: Na 3 N sodium nitride KBr Al 2 O 3 MgS potassium bromide aluminum oxide magnesium sulfide

Learning Check A. The formula for the ionic compound of Na + and O 2- is 1) NaO 2) Na 2 O 3) NaO 2 What is the name of the compound? B. The formula of a compound of aluminum and chlorine is 1) Al 3 Cl 2) AlCl 2 3) AlCl 3 What is the name of the compound?

Solutions A. The formula for the ionic compound of Na + and O 2- is 2) Na 2 O The name is sodium oxide B. The formula of a compound of aluminum and chlorine is 3) AlCl 3 The name is aluminum chloride

Transition Metals with More than One Combining Capacity If the metal has more than one combining capacity, the specific combining capacity being used must be given in the name as a ROMAN NUMERAL in brackets after the metal name. Copper can be Cu +1 or Cu +2 Iron can be Fe +2 or Fe +3 Lead can be Pb +2 or Pb +4 There are others as well see the Per. Table or p. 341 in Hebden (Cations).

Naming Transition Metal Salts Use a roman numeral after the name of a transition metal that possesses multiple combining capacities 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 O SnCl 4 Fe 2 O 3 CuS copper ( ) oxide ( )

Solutions Complete the names of the following binary compounds with variable metal ions: FeBr 2 iron ( II ) bromide Cu 2 O SnCl 4 Fe 2 O 3 CuS copper ( I ) oxide tin (IV) chloride iron (III) oxide copper (II) sulfide

Learning Check Name the following compounds: A. CaO - hint: does Ca have only one cc, or multiple cc? Do you need a roman numeral?? 1) calcium oxide 2) calcium(i) oxide 3) calcium (II) oxide B. SnCl 4 1) tin tetrachloride 2) tin(ii) chloride 3) tin(iv) chloride C. Fe 2 O 3 1) iron oxide 2) iron (III) oxide 3) iron trioxide

Solutions Name the following compounds: A. CaO 1) calcium oxide B. SnCl 4 3) tin(iv) chloride C. Fe 2 O 3 2) iron (III) oxide

Polyatomic Ions There are groups of atoms that tend to stay together (very stable) and carry an overall charge These groups are called polyatomic ions There is a list of polyatomic ions in the back of your Hebden text or on the back of your periodic table All polyatomic ions except ammonium NH 4 + have negative charges and act as nonmetals Notice that many have an ate or ite ending this can alert you that you are dealing with a polyatomic ion

The charge on the polyatomic ions are also their combining capacity. Write the formula for the compound made with sodium and carbonate: Na + CO -2 3 Na + the formula is Na 2 CO 3 We needed one more Na + to balance charges

If you end up with two or more polyatomic ions in your formula, you need brackets!! Find the formula for the compound that has calcium and hydroxide Ca 2+ OH OH The formula is Ca(OH) 2

Naming Compounds with Polyatomic Ions Name like you would any other ionic compound but DON T change the ending of the polyatomic ion Ca(OH) 2 is.. calcium hydroxide FeCO 3 is iron (II) carbonate

Complete the Ionic Formula Writing/ Naming worksheet. Complete the Polyatomic Ions worksheet.

This won t get you anywhere!