The Nonmetal-Nonmetal

vs Metal – Nonmetal Bond

Lewis Dot Structures

• A famous chemist named Lewis invented a symbol to show valence electrons. He used a dot next to the symbol to represent each valence electron. The dots are spread around the 4 sides.

• Each pair of dots

Represents a bond.

Covalent Bonds•What is a Covalent Bond?

- A covalent bond is a chemical bond resulting from SHARING of electrons between 2 nonmetals.

•?

Covalent Bonds can have multiple bonds, so you should be familiar with the following…

Single Covalent Bond- chemical bond resulting from sharing of an electron pair between two atoms. H2O

Double Covalent Bond- chemical bond resulting from sharing of two electron pairs between two atoms. CO2

Triple Covalent Bond-chemical bond resulting from sharing of three electron pairs between two atoms. N2

Types of Covalent Bonds• Two types of colvalent bonds: nonpolar and

polar

• Recall electronegativity (desire for electrons) -see shaded table on ole yeller

• The electronegativity difference between the two atoms determines whether it is a nonpolar or polar bond.

Electronegativity difference:

0 .4 2.0

Nonpolar Polar Ionic

Polar BondsA nonpolar bond tends to share electrons equally

A polar bond means there is a dipole or one pole (end) with a positive charge and one pole (end) with a negative charge, therefore they tend to stick together better since their opposite charges attract. (=)(-)

Very strong polar bonds are

ionic bonds like NaCl

Covalent Bonds Do NOT have ions or need to Balance Charges

• They use prefixes to show the number of atoms:

• Mono-• Di-• Tri-• Tetra-

• Examples:

• H2O =

dihydrogen monoxide

• CO2 = carbon dioxide

• dinitrogen tetraoxide = N2O4

• Phosphorus trichloride = PCl3

Pop Quiz: Covalent Bonds:HOT or NOT?

HOT, for sure!If Miley says it’s hot, it’s HOT!

When a metal and nonmetal come together, a pair of electrons acts as a

bond and they each become ions.

Ionic Bonding Rules:• Metal first, nonmetal second• Nonmetal ion becomes ‘ide’• Metal is positive, nonmetal is negative• Charges must balance to zero• Formula uses a subscript to balance

charges• Example: MgCl2 ; Na2O; NaCl

The sodium atom and chloride atom bond together as ions and form a new

compound.

This is called an ionic bond.

Practice:Sodium and fluorine

Barium and iodine

lithium and phosphorus

Aluminum and oxygen

Beryllium and oxygen

Calcium and nitrogen

Answers:Sodium and

fluorine

sodium fluoride

NaF

Barium and iodine

barium iodide

BaI2

lithium and phosphorus

lithium phosphide

Li3P

Aluminum and oxygen

aluminum oxide

Al2O3

Beryllium and sulfur

beryllium sulfide

BeS

Calcium and nitrogen

calcium nitride

Ca3N2

Solutions

• When ionic compounds are put in water, they dissolve into ions:

Polyatomic ions: are groups of atoms bonded together with a charge hence the name “poly”

“atomic” “ions”. • Examples:

• OH-1 = hydroxide

• NO3-1 = nitrate

• PO4-3 = phosphate

• SO4-2 = sulfate

*They behavejust like single atom

ions.

Practice: Use polyatomic ions just like any other ion; But when you

have more than one , use parentheses.

• barium hydroxide= (Notice parentheses show multiple

ions.)

barium hydroxide= Ba OH

+2 -1

Ba(OH)2

+2 -1(2) = 0

• strontium nitrate =

• strontium nitrate = Sr NO3

+2 -1

strontium nitrate = Sr(NO3)2

+2 + -1(2)

• lithium phosphate

• lithium phosphate = Li PO4

+1 -3

lithium phosphate Li3PO4

+1(3) + -3 = 0

potassium sulfate

• potassium sulfate = K SO4

+1 -2

potassium sulfate = K2SO4

+1(2) + -2 = 0

Transition metals: Metals that have more than one possible

charge: • Cobalt: Co+2, Co+3

• Copper: Cu+, Cu+2

• Iron: Fe+2, Fe+3

• Lead: Pb+2, Pb+4

• When writing the names, always use roman numerals to show the charge.

Examples:

• Cobalt (II) Co+2, Cobalt (III) Co+3

• Copper(I), Cu+, or Copper (II), Cu+2

• Iron(II) Fe+2, or iron (III), Fe+3

• Lead(II), Pb+2, or lead (IV), Pb+4

• Each different charged ion behaves completely different than the other! The charges matter!

Practice!

Lead (IV) hydroxide

• Lead(IV) hydroxide = Pb(OH)4

• Copper (II) nitrate

• Copper(II) nitrate = Cu(NO3)2

+2 -1

• CoPO4

• CoPO4 = Cobalt (III) phosphate

+3 -3

• Fe2(SO4)3

+3 -2Iron (III) sulfate Fe2(SO4)3

HydratesSome ionic compounds absorb water molecules

into their structures. These are called hydrates. NaCl•2H2O is the symbol for sodium chloride dihydrate. Notice the prefix di- means 2 water molecules.

Name these hydrates: MgSO4•5H2O

CuCl2•4H2O

Finding Percentage of Waterin a Hydrate

You can find the percentage of water in a hydrate by dividing the mass of the water by the total mass times 100.

Lets take NaCl•2H2O

Using the periodic table, the mass of Na=23, Cl=35.5, H2O = 18. Total mass with 2 H20 is 94.4

Water mass (36)/ Total (94.4) x 100

= 38 % water

What are the differences between ionic bonding and covalent bonding? List them below:

Differences:

Ionic• Metal , nonmetal-ide• Balance charges using

subscripts• Polyatomic ions use

parentheses in multiples• Transition metals use

roman numerals to show charge

Differences:

Covalent• Two nonmetals• Nonmetal, nonmetal-

ide• No ions- they share e-• Use prefixes• Don’t need to balance

Differences:

Ionic• Metal , nonmetal-ide• Balance charges using

subscripts• Polyatomic ions use

parentheses in multiples• Transition metals use

roman numerals to show charge

Covalent• Two nonmetals• Nonmetal, nonmetal-

ide• No ions- they share e-• Use prefixes• Don’t need to

balance

Ionic bonds: HOT or NOT?

Definitely HOT Baby!