Chapter 5 Naming Compounds Writing Formulas Systematic Naming

Chapter 5 Naming Compounds Writing Formulas

Systematic Naming There are too many compounds to remember the names of them all. l Compound is made of two or more elements. l Put together atoms. l Name should tell us how many and what type of atoms. l

Periodic Table More than a list of elements. l Put in columns because of similar properties. l Each column is called a group. l

1 A Representative 2 A l The group A elements 5 A 7 A 3 A 4 A 6 A 0

Metals

Metals Luster – shiny. l Ductile – drawn into wires. l Malleable – hammered into sheets. l Conductors of heat and electricity. l

Transition metals l The Group B elements

Dull l Brittle l Nonconductorsinsulators l Non-metals

Metalloids or Semimetals Properties of both l Semiconductors l

Atoms and ions Atoms are electrically neutral. l Same number of protons and electrons. l Ions are atoms, or groups of atoms, with a charge. l Different numbers of protons and electrons. l Only electrons can move. l Gain or lose electrons. l

Anion A negative ion. l Has gained electrons. l Non metals can gain electrons. l Charge is written as a super script on the right. l -1 F -2 O Has gained one electron Has gained two electrons

Cations Positive ions. l Formed by losing electrons. l More protons than electrons. l Metals form cations. l +1 K Has lost one electron +2 Ca Has lost two electrons

Compounds Follow the Law of Definite Proportion. l Have a constant composition. l Have to add the same number of atoms every time. l Two types. l

Two Types of Compounds 1 Molecular compounds Made of molecules. l Made by joining nonmetal atoms together into molecules. l

Two Types of Compounds 2 Ionic Compounds Made of cations and anions. l Metals and nonmetals. l The electrons lost by the cation are gained by the anion. l The cation and anions surround each other. l Smallest piece is a FORMULA UNIT. l

Two Types of Compounds Smallest piece Types of elements State Melting Point Ionic Molecular Formula Unit Molecule Metal and Nonmetals solid Solid, liquid or gas High >300ºC Low <300ºC

Chemical Formulas Shows the kind and number of atoms in the smallest piece of a substance. l Molecular formula- number and kinds of atoms in a molecule. l CO 2 l C 6 H 12 O 6 l

Formula Unit The smallest whole number ratio of atoms in an ionic compound. l Ions surround each other so you can’t say which is hooked to which. (pg 91) l

Charges on ions For most of the Group A elements, the Periodic Table can tell what kind of ion they will form from their location. l Elements in the same group have similar properties. l Including the charge when they are ions. l

+1 +2 +3 -3 -2 -1

What about the others? We have to figure those out some other way. l More on this later. l

Naming ions We will use the systematic way. l Cation- if the charge is always the same (Group A) just write the name of the metal. l Transition metals can have more than one type of charge. l Indicate the charge with roman numerals in parenthesis. l

Name these Na+1 l Ca+2 l Al+3 l Fe+2 l Pb+2 l Li+1 l

Write Formulas for these Potassium ion l Magnesium ion l Copper (II) ion l Chromium (VI) ion l Barium ion l Mercury (II) ion l

Naming Anions are always the same. l Change the element ending to – ide l F-1 Fluorine l

Naming Anions are always the same. l Change the element ending to – ide l F-1 Fluorin l

Naming Anions are always the same l Change the element ending to – ide l F-1 Fluori l

Naming Anions are always the same l Change the element ending to – ide l F-1 Fluor l

Naming Anions are always the same l Change the element ending to – ide l F-1 Fluori l

Naming Anions are always the same l Change the element ending to – ide l F-1 Fluoride l

Naming Anions are always the same l Change the element ending to – ide l F-1 Fluoride l

Name these Cl-1 l N-3 l Br-1 l O-2 l Ga+3 l

Write these Sulfide ion l iodide ion l phosphide ion l Strontium ion l

Polyatomic ions Groups of atoms that stay together and have a charge. l Acetate C 2 H 3 O 2 -1 l Nitrate NO 3 -1 l Nitrite NO 2 -1 l Hydroxide OH-1 l Permanganate Mn. O 4 -1 l Cyanide CN-1 l

Polyatomic ions Sulfate SO 4 -2 l Sulfite SO 3 -2 l Carbonate CO 3 -2 l Chromate Cr. O 4 -2 l Dichromate Cr 2 O 7 l -2 Phosphate PO 4 -3 l Phosphite PO 3 -3 l l Ammonium NH 4+1

Ions in Ionic Compounds

Naming Ionic Compounds • Cations: • Representative – use name • D-Block – use Roman Numeral Anions: • Element – name + -ide Polyatomic – name with -ite or -ate Check Balance

Naming Binary Ionic Compounds Binary Compounds - 2 elements. l Ionic - a cation and an anion. l To write the names just name the two ions. l Easy with Representative elements. l Group A l Na. Cl = Na+ Cl- = sodium chloride l Mg. Br 2 = Mg+2 Br- = magnesium bromide l

Naming Binary Ionic Compounds The problem comes with the transition metals. l Need to figure out their charges. l The compound must be neutral. l same number of + and – charges. l Use the anion to determine the charge on the positive ion. l

Naming Binary Ionic Compounds Write the name of Cu. O l Need the charge of Cu l O is -2 l copper must be +2 l Copper (II) chloride l Name Co. Cl 3 l Cl is -1 and there are three of them = -3 l Co must be +3 Cobalt (III) chloride l

Naming Binary Ionic Compounds Write the name of Cu 2 S. l Since S is -2, the Cu 2 must be +2, so each one is +1. l copper (I) sulfide l Fe 2 O 3 l Each O is -2 3 x -2 = -6 l 3 Fe must = +6, so each is +2. l iron (III) oxide l

Naming Binary Ionic Compounds Write the names of the following l KCl l Na 3 N l Cr. N l Sc 3 P 2 l Pb. O 2 l Na 2 Se l

Ternary Ionic Compounds Will have polyatomic ions l At least three elements l name the ions l Na. NO 3 l l Ca. SO 4 l Cu. SO 3 l (NH 4)2 O

Ternary Ionic Compounds Li. CN l Fe(OH)3 l (NH 4)2 CO 3 l Ni. PO 4 l

Writing Ionic Formulas • Cations: • Representative – use name • D-Block – use Roman Numeral Anions: • Element – name + -ide Polyatomic – name with -ite or -ate Check Balance

Writing Formulas The charges have to add up to zero. l Get charges on pieces. l Cations from name of table. l Anions from table or polyatomic. l Balance the charges by adding subscripts. l Put polyatomics in parenthesis. l

Writing Formulas Write the formula for calcium chloride. l Calcium is Ca+2 l l Chloride is Cl-1 Ca+2 Cl-1 would have a +1 charge. l Need another Cl-1 l Ca+2 Cl 2 -1 l

Write the formulas for these Lithium sulfide l tin (II) oxide l tin (IV) oxide l Magnesium fluoride l Copper (II) sulfate l Iron (III) phosphide l gallium nitrate l Iron (III) sulfide l

Write the formulas for these Ammonium chloride l ammonium sulfide l barium nitrate l

Things to look for If cations have (), the Roman Numeral number is their charge. l If anions end in -ide they are probably off the periodic table (Monoatomic) l If anion ends in -ate or -ite it is polyatomic anion l