Forming Forming CompoundsCompounds

Ionic vs. CovalentIonic vs. Covalent

Understanding how atoms Understanding how atoms of elements combineof elements combine

when two atoms when two atoms collide,collide, valence electrons valence electrons on each atom interacton each atom interact

Chemical bonds form if their valence e- Chemical bonds form if their valence e- make a make a new arrangement with a lower new arrangement with a lower energy energy than their previous arrangementthan their previous arrangement

For many atoms, the lowest energy For many atoms, the lowest energy arrangement is the same as the closest arrangement is the same as the closest noble gasnoble gas

Atoms achieve noble gas electron Atoms achieve noble gas electron configuration byconfiguration by losing/gaining/sharing losing/gaining/sharing electronselectrons

What is a bond?What is a bond? A bond is an attachment among A bond is an attachment among

atomsatoms Atoms may be held together for Atoms may be held together for

several several

COMPOUNDS and their BONDS

Ionic Compounds Covalent Compounds

Ionic Bonds

Metals

Covalent Bonds

Nonmetals

Nonmetals

Ionic CompoundsIonic Compounds Consist of Consist of positive ion + negative ionpositive ion + negative ion Ions held together by Ions held together by strong attractionstrong attraction

b/w b/w oppositely chargedoppositely charged ions = ions = IONIC BONDIONIC BOND Chemical and physical properties of the Chemical and physical properties of the

ionic compound are different from those of ionic compound are different from those of the individual elementsthe individual elements

Ex) Na Ex) Na soft, shiny metalsoft, shiny metal Cl Cl yellow, poisonous gasyellow, poisonous gas NaCl white, crystalline (table salt) NaCl white, crystalline (table salt)

Charge Balance in Ionic Charge Balance in Ionic CompoundsCompounds

Chemical Formula indicates:Chemical Formula indicates: Number of ionsNumber of ions

Kind of ions Kind of ions that make the ionic compoundsthat make the ionic compounds

Ex) NaClEx) NaCl MgMg22OO

Nearly all ionic compounds involve bonds b/wNearly all ionic compounds involve bonds b/w metal cations + nonmetal anionsmetal cations + nonmetal anions

positive negativepositive negativecharge chargecharge charge

• The sum of The sum of ionic chargesionic charges = zero = zero (total positive charges = total negative charges)(total positive charges = total negative charges)

Properties of Ionic CompoundsProperties of Ionic CompoundsCations and anions form a regular repeating pattern

creates a characteristic crystalline shape

Strong attraction b/w charged ions extends throughout crystal relatively high melting points

When molten or dissolved in water, ions move freely

Conduct electricity in liquid

In solid state, ions unable to move Not electrical conductors in solid state

Subscripts in FormulasSubscripts in FormulasIonic compounds made of 2 elements are Ionic compounds made of 2 elements are

called called binary compoundsbinary compoundsCompounds that lose/gain more than 1 electron Compounds that lose/gain more than 1 electron

need to bond to more than 1 atom need to bond to more than 1 atom

Writing Ionic Formulas from Ionic Writing Ionic Formulas from Ionic ChargesCharges

Subscripts represent the # of positive and negative ions Subscripts represent the # of positive and negative ions that give an overall charge of zerothat give an overall charge of zero

Use the ionic charges to write the formulaUse the ionic charges to write the formula

* The cation is always written first, followed by the * The cation is always written first, followed by the subscriptsubscript

Practice Naming Ionic Practice Naming Ionic CompoundsCompounds

The International Union of Pure and The International Union of Pure and Applied Chemistry (IUPAC) Applied Chemistry (IUPAC) a a global global organization of scientists organization of scientists They set They set standardsstandards in chemistry in chemistry

Each compound has a unique name Each compound has a unique name

The formula of the compound reflects its The formula of the compound reflects its namename

Naming Ions

Monatomic IonsIons consisting of a single atom with a

(+) or (--) charge due to gaining or losing valence electrons.

*Noble Gases do not form ions! (They have complete valence shells

already)

Cations (+)Cations (+) MetalsMetals Most from Groups 1A, 2A, 3AMost from Groups 1A, 2A, 3A Naming: Naming:

Same as the name of the metal, Same as the name of the metal, followed by ion or cationfollowed by ion or cation

Example: Sodium Ion, Potassium IonExample: Sodium Ion, Potassium Ion

Anions (-)Anions (-) Non-metalsNon-metals Most from 5A, 6A, 7AMost from 5A, 6A, 7A Naming: Naming:

Start with the Start with the stemstem of the element’s of the element’s name ending with -idename ending with -ide

Example: Example: FluorFluoride, ide, ChlorChloride, ide, NitrNitrideide

Naming Binary Ionic Naming Binary Ionic CompoundsCompounds

metalmetal + + nonmetalnonmetal always 1always 1stst always 2ndalways 2nd

EElemental lemental ++ Elemental + - Elemental + -ideide ending ending Name NameName Name

NaNa ++ F F SodiumSodium Fluorine Fluorine

NaNaFF Sodium Sodium fluorfluorideide* Subscripts are never mentioned in ionic compounds. * Subscripts are never mentioned in ionic compounds.

They are understood as a They are understood as a result of the charge balance of the ions in the compoundresult of the charge balance of the ions in the compound

Practice Naming Binary Ionic Practice Naming Binary Ionic CompoundsCompounds

Write the name of each of the following Write the name of each of the following ionic compounds.ionic compounds.

a) Naa) Na22OO b) Mgb) Mg33NN22

Compound Compound Ions and Names Name of CompoundIons and Names Name of Compounda)a) NaNa22OO Na Na++ OO2-2-

SodiumSodium OxideOxide Sodium oxide Sodium oxidea)a) MgMg33NN22 Mg Mg 2+2+ NN3-3-

MagnesiumMagnesium Nitride Magnesium Nitride Magnesium nitride nitride

Metals with Variable ChargeMetals with Variable Charge Transition metalsTransition metals typically form typically form

two or moretwo or more kinds of positive ions kinds of positive ions because they lose their outer because they lose their outer electrons from a lower levelelectrons from a lower level

For these metals, it is not possible to For these metals, it is not possible to predict the ionic charge from the predict the ionic charge from the group numbergroup number

This is called This is called variable valencevariable valence

Transition ElementsTransition Elements Metals from Groups 3 – 12 Metals from Groups 3 – 12 Nearly all form more than one cationNearly all form more than one cation Ex) Fe (iron) forms Fe Ex) Fe (iron) forms Fe 2+2+ and Fe and Fe 3+3+

Use the Use the reverse cross-over method to determine the charge on to determine the charge on the cation and write formulas for the the cation and write formulas for the ionic compoundsionic compounds

Two Methods – Stock vs. Classical SystemsStock System

Use roman numerals in parentheses to identify the charge of the ion

Example: Fe2+ Written: Iron(II) ion Read: “Iron two ion,”

Example: Cr2+ Written: Chromium(II) ionRead: “chromium two ion”

Transition Metals

Transition MetalsClassical System

A suffix is used with root name to name the ion

Example: Fe2+ Written: Ferrous Ion

Example: Fe3+ Written: Ferric Ion

Example: Cr2+Written: Chromous Ion

Example: Cr3+Written: Chromic Ion

Transition MetalsClassical System: some names may seem

unfamiliarIron: Ferr-Copper: Cupr-Tin: Stann-Lead: Plumb-

Some transition metals have only one chargeAg+

Cd2+

Zn2+

Determining the charge on a Determining the charge on a cation:cation:

Example 1) FeCl3

Fe 3+ Cl-

• The charge on the chloride anion is correct.• Therefore the charge on the cation is correct.

Example 2) FeO

Fe+ O-

• The anion charge is incorrect.• Doubling the charges on both ions gives the

correct charges.

Some common ions and their Some common ions and their location on the periodic tablelocation on the periodic table

Practice Naming Ionic Practice Naming Ionic CompoundsCompounds

Write the name for each of the following ionic compounds:

a. FeO Reverse Cross-over

Fe charge + O2- charge = 0Fe O ? + (2-) = 0 Fe1+ O1-

(2+) + (2-) = 0 2x(Fe1+)(O1-)

Fe2+ O2-

Stock System Classic SystemIron (II) oxide Ferrous oxide

b. Cu2S Reverse Cross-Over

2(Cu charge) + S2- charge = 0 Cu2 S 2(?) + (2-) = 0Cu1+ S2-

2(1+) + (2-) = 0

Stock System Classic System Copper (I) sulfide Cuprous

sulfide

Polyatomic Ions Ions composed of more than one atom Tightly bound groups of atoms that

behave as one unit and have a charge All Anions ending in -ite or -ate contain

Oxygen “-ites” have one less oxygen than “-ates”Examples: ClO2- Chlorite

ClO3- ChlorateCr2O7

2- DichromatePO3

3- Phosphite

Polyatomic Ions

When a polyatomic ion contains Hydrogen,

it is like adding a H+ with another polyatomic ion

Examples: H+ + CO32- ----> HCO3

-

Carbonate Hydrogen Carbonate

H+ + PO43- ----> HPO4

2-

Phosphate Hydrogen Phosphate

Binary Ionic CompoundsAn ionic or molecular compound

composed of two elements

Naming: Place the cation first followed by the anion.Formula: Cation first, Anion second

Remember, total charge equals zero!

Example: Cs2O = Cesium Oxide (Ionic)CuO = Copper(II) Oxide (Ionic) Hint: 1:1 ratio

Naming and Writing FormulasBinary Ionic Compounds

Naming and Writing FormulasCompounds with Polyatomic Ions

Recall that a Polyatomic Ion acts as one unit

Naming: Place the cation first followed by the anion.

Formula: Cation first, Anion second

Example: PbSO4 = Lead(II) Sulfate

K2HPO4 = Potassium Hydrogen Phosphate

Naming and Writing Formulas

Compounds with Polyatomic Ions

Naming Chemical Compounds

Guidelines:1) -ide generally indicates a binary

compound2) -ite or -ate means a polyatomic ion

that includes O3) A Roman numeral shows the charge of

the cation4) Prefixes generally indicate a molecular

compound