Chapters 3 Ionic Compounds

Octet Rule Octet Rule: the tendency for atoms to achieve 8 electrons in their valence shell Natural electron configuration of the Noble Gases Done by gaining, losing, or sharing electrons Increases stability, less chance to react afterwords H and He seek a “Duet” Na = [Ne]3s1  Na+ = [Ne] Cl = [Ne]3s23p5  Cl- = [Ne]3s23p6 = [Ar]

To gain or to lose electrons? Goal is to achieve a noble gas electron configuration Metals lose electrons Nonmetals gain electrons Its easier for a nonmetal (Ex: chlorine) to gain 1 electron vs losing 7 electrons. Its easier for a metal (Ex: magnesium) to lose 2 electron vs gaining 6 electrons. To gain or to lose electrons?

Ionic Bonding Ions: atoms that have a charge due to gain or loss of electrons Anion: (-) charged atom – added electron(s) Cation: (+) charged atom – lost electron(s) Ionic Bond: a bond formed through the transfer of one or more electrons from one atom or group of atoms to another atom or group of atoms

Oxidation state oxidation state/number – represents the number of electrons lost or gained by an atom of an element in that compound It relates to the charge of the atom as well If a sodium atom loses one electron it will have a positive charge and the oxidation state will be +1 If an oxygen atom gains two electrons it will have a negative charge and the oxidation state will be -2

Oxidation state Formula Unit

Oxidation state

Ionic Compounds: compounds composed of oppositely charged ions that are held together by their attraction to each other Metal + Non-metal NaCl Metal + Polyatomic Ion NaNO3 Polyatomic Ion + Non-metal NH4Cl Polyatomic Ion + Polyatomic Ion NH4NO3 Net charge on compound equal to zero

Oxyanions SO42- Sulfate SO32- Sulfite PO43- Phosphate PO33- Phosphite NO3- Nitrate NO2- Nitrite ClO4- Perchlorate ClO3- Chlorate ClO2- Chlorite ClO- Hypochlorite

Rules For Naming Ionic Compounds Name the cation by its elemental/polyatomic name Na+Cl- = NaCl = sodium chloride If the metal is a transition metal with a variable charge, use a Roman Numeral in parentheses for its charge FeCl2 = iron(II)chloride Next, name the anion and change its ending to “-ide” Cl- = chloride If the anion is polyatomic, do not change the ending to “-ide” NaNO3 = sodium nitrate Do NOT use prefixes (mono, di, tri etc.) to indicate how many of each atom are present

Iron (III) Chloride Iron (II) Chloride FeCl3 FeCl2

Problems Write the name for the following compounds: KI MgBr2 Al2O3 FeCl2 CaSO4 Ba(NO2)2 Cu(NO3)2 potassium iodide magnesium bromide aluminum oxide iron(II)chloride calcium sulfate barium nitrite copper(II) nitrate

Write the Formula for the following ionic compounds: Sodium Fluoride Calcium Sulfite Calcium Chloride Iron (III) Oxide Cobalt (II) Hydroxide Ammonium Bromide Ammonium Carbonate Aluminum Carbonate NaF CaSO3 CaCl2 Fe2O3 Co(OH)2 NH4Br (NH4)2CO3 Al2(CO3)3

Chapter 3 checklist Know how to write electron configurations for main group element ions Know the octet rule and the duet exception Know what kind of an ion an element will become based on its group number Know what ionic bonding is Know the oxidation state of an ion Know how to find the charge of a transition metal based on the ion it is attached to Know what an ionic compound is and how to make one Know all the names, formulas and charge of the major polyatomic ions Know how to name an ionic compound from the formula Know how to produce a formula from the name of an ionic compound