welcome back!! this semester… january- bonding and naming ionic and covalent compounds...

Welcome Back!!• This semester…• January- Bonding and Naming Ionic

and Covalent Compounds• Jan/February- Finish Bonding &

Reactions• After Feb. break- Stoichiometry• March/April- Thermo, Gases• April- Acids and Bases• May- Solutions & Final Exam Review

Chemical Bondingand

Nomenclature

Valence electrons• The electrons in the highest energy level of

an atom.• s and p electrons*• *d electrons are never valence electrons

• Total # of s and p electrons

in a “FULL” energy level = 8

(THE OCTET RULE)

Lewis Structures

• We include only valence electrons

Water

How many valence electrons?

LEWIS DOT STRUCTURES FOR THE FIRST 20 ELEMENTS

Bonding• Chemical bond:

• A force that holds groups of two or more atoms together and makes them function as a unit

• Fundamental types of bonds• Ionic• Covalent• Metallic

• Bonds form in order to achieve a full outer shell (8) of electrons to:• Decrease potential energy (PE)• Increase stability

Ionic bonding• Described as a TRANSFER OF

ELECTRONS• Takes place between metals and

nonmetals. Nonmetals “want” electrons and metals “want” to give electrons away.

• Atoms become ions by gaining or losing electrons

• Oppositely charged ions are attracted to one another: this attraction is an “ionic bond.”

• Results in an ionic COMPOUND

Metals and Nonmetals Create Ionic Bonds

Ions

• Cation• Positively charged• Atom has LOST one or more

electrons• Metals tend to become cations

• Anion• Negatively charged• atom has GAINED one or more

electrons• Nonmetals tend to become anions

Types of ions

• Monatomic ion• Cation or anion that consists of a

single type of element• Ex: Li+, Br-

• Polyatomic ion• 2 or more elements that are

combined, but act as a single ion (or particle)

• Ex: CO32- or NH4

+

Formula units• Ionic compounds are represented by

formula units: similar to “molecule” except ionic compounds exist as a 3D network of multiple formula units because of the electrostatic attraction of opposite charges.

• The lowest whole number ratio of ions in an ionic compound is a formula unit.

NaClCaO

MgCl2

Al2O3

Types of ionic compounds

COMPOUND

TernaryCompound

BinaryCompound

2 elements

more than 2Elements

Means there is a Polyatomic ion present

NaNO3NaCl

Rule of Zero Charge• The charges on the metal cations (+)

and nonmetal anions (-) add up to zero.• Ex: Na+ and Cl- add up to an overall

charge of zero, so the formula unit is NaCl

• Ex: Ca2+ and O2- add up to an overall charge of zero, so the formula unit is CaO

Writing Binary Ionic Compounds

• RULES:

****Cation always listed first****

1. Drop Charges

2. Criss Cross Apple Sauce

3. Reduce (simplify) subscripts if needed

• Na+ and Cl- NaCl

What if the charges are opposite, but not equal???

• Criss-cross the charge values to subscripts• Ex: Al3+ + O2- is represented as Al2O3

• Ex: Mg2+ + Cl- is represented as MgCl2

• But why?• Because the overall charge

must be zero• All atoms “want” a full valence

Naming Binary ionic compounds

1. List name of cation• If metal cation is not a transition

element, give it the same name as the element and move on to anion.

• If cation can have more than one charge (i.e. most transition metals), use roman numerals in parentheses to specify charge.

For Example:Iron has 2 common oxidation states (charges): Fe2+ and Fe3+

• Fe2+ would be iron (II)• Fe3+ Would be iron (III)

CaO

Fe2O3

Naming Binary ionic compounds

• Name the cation first• Name the anion last; for binary

compounds, it always ends in –ide.

• Examples:

CaO would be calcium oxide

Fe2O3 is iron (III) oxide

NaCl is sodium chloride

AgCl is silver chloride

Common anion endings

• P- phosphide F-fluoride

• O-oxide Br- bromide

• S- sulfide I- iodide

• Cl-chloride C- carbide

• N-nitride

Some common polyatomic ions

Polyatomic Ions- QUIZ Friday!!• Add these to your list:

• bromate, BrO3-

• iodate, IO3-

• thiocyanate, SCN -

• hydrogen carbonate, HCO3- (also

called bicarbonate)• hydride, H- is NOT part of the list to

memorize

• THERE ARE 26 to memorize

Naming polyatomic anions: these just have to be memorized!

• With anions that end in oxygen, if you know one , you can figure out the other!

# of oxygens naming convention

1 less (PO33-) ends in –ite(phosphite)

1 more (PO43-) ends in –ate(phosphate)

Notice that within one group of polyatomic ions, the charges are the same!

Writing formulas for ternary compounds

• If more than 1 of a polyatomic ion is present, write parentheses around any polyatomic ion and add subscripts to the outside of the parentheses.

• Never change the subscript of a polyatomic ion (it will change the composition of the ion):• Ca(OH)2, Ca3(PO4)2

• Include the subscript inside the parentheses

Naming ternary ionic compounds

• For a monatomic cation and polyatomic anion, write both names together; do not change them in any way

• Ex: Na2SO4 is sodium sulfate

• For a polyatomic cation with a monatomic anion, write the polyatomic ion’s name first, then the monatomic root with the –ide ending

• Ex: NH4Cl is ammonium chloride

Metallic Bonding

• Metals form lattices but do not lose, gain, or share e-

• Outer e- shells overlap = electron sea model

• e- are free to move = delocalized e- making a metallic cation

• Metallic bond: attraction of a metallic cation for delocalized electron

• Properties of metals: melting point varies greatly, malleable, ductile, good conductors

Sea of electrons

Ionic Metallic

• Electron sea model – delocalized electrons attracted to metal cations

• Malleable, ductile, lustrous, colorful

• Conducts electricity

• Overall highest MP of 3 types

All bonding involves valence

electrons

Both involve metals

• Oppositely charged ions attracted to each other (cations and anions)

• Metals with non-metals

• Brittle, dull solids

• Only conducts electricity as electrolytes

• Generally, medium MP of 3 types

Covalent bonding

Covalent bonds

• Occur between atoms that are “sharing” electrons• Form covalent compounds

QUIZ: 1-5, NAME THE COMPOUND…6-10, WRITE THE FORMULA1) SrO

2) NaClO3

3) AlF3

4) NH4OH

5) Fe3(PO3)2

6) barium nitrite

7) potassium chloride

8) manganese (II) iodide

9) copper (II) acetate

10) sodium carbonate