chapter 8 notes mr nelson 2010. chemical bonds three basic types of bonds –ionic electrostatic...

Chapter 8 Notes

Mr Nelson 2010

Chemical Bonds• Three basic types of bonds

– Ionic• Electrostatic attraction between

ions

– Covalent• Sharing of electrons

– Metallic• Metal atoms bonded to several

other atoms

Ionic Compounds – Review

• Made up of ions– Cations (+) & Anions (-)– Metals & Nonmetals (or polyatomic ions)

• Exchange of electrons

• Charges Balance

Molecular Compounds – Intro

• No ions– Charges will not balance– Composed of two nonmetals

• Sharing of electrons– Covalent bonding

• Naming is based on prefixes

Nomenclature of Binary Compounds

• If both elements are nonmetals we must use prefixes.

• The 1st element only gets a prefix if it is greater than 1.

• 2nd element always gets a prefix and change the ending to -ide

Nomenclature of Binary Compounds

• Example of a molecular comp:

• CO2

• CO

• CCl4

Practice

• PCl5 dihydrogen monoxide

• SF6 carbon trichloride

• N2O disulfur hexoxide

• NO2 nitrogen triiodide

Naming Acids

• An acid is any compound that starts with a hydrogen

• When naming an acid:– 1st locate the anion (- charge)

Acid Nomenclature

• If the anion in the acid ends in –ide (not PI)

• change the ending to -ic acid and add the prefix hydro-

hydro________ic acid

– HCl

Acid Nomenclature

• If the anion in the acid ends in –ate (all PI’s)

• change the ending to -ic acid.

___________ic acid

– HClO3

Acid Nomenclature• If the anion in the acid ends in –ite (all PI’s) • change the ending to -ous acid.

_________ous acid

– HClO2

Acids – Finishing Up• If you have the name and need to find the formula

– Example: Acetic Acid– Cross off the –ic and add at –ate

– Acetate! = C2H3O2-

• Finish by adding the correct # of H’s (1 for every negative)

• HC2H3O2 is acetic acid

Warm Up

• HBr Chlorous Acid

• FeS Copper(I) fluoride

• PBr5 dinitrogen dioxide

• K2SO4 nitrogen monoxide

• CCl4 hydroiodic acid

• HNO3 potassium nitrate

• LiCl phosphoric acid

Covalent Bonding• Covalent bond – atoms share electrons.

• There are several electrostatic interactions in these bonds:– Attractions between electrons and nuclei

– Repulsions between electrons

– Repulsions between nuclei

Lewis Dot Structures

• ONLY Valence (outer) electrons are involved.

• Lewis dot structures can be drawn for:– atoms – molecules

• Lewis dot structures show structure of a molecule, and help predict shape.

Steps to Writing Lewis Structures1. Find the sum of valence

electrons of all atoms in the polyatomic ion or molecule.

PCl3

5 + 3(7) = 26

Writing Lewis Structures

2. Arrange element symbols to show how atoms are connected – show electrons as dots.

Draw in the valence electrons of each of the atoms

Keep track of the electrons:

Writing Lewis Structures

3. Connect the lines to form single bonds. 1 line = 2 electrons

Keep track of the electrons:

Writing Lewis Structures

4. Finish by checking for octets. Hydrogen only needs

2 electrons to be happy

Keep track of the electrons:

Writing Lewis Structures

5. If the central atom does not have an octet…

…form multiple bonds until it does. Example: HCN

Exceptions!

• Boron and Aluminum are okay with only 6 e- around them– BF3

Exceptions

• If the Lewis Dot Structure you are drawing is an ion: – Use [] and specify the charge– Add or subtract electrons

• Positive charges take away electrons

• Negative charges add electrons

• Example: Br-