Chapter 9 Notes

Mr Nelson 2009

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: hydrochloric acid

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

_________ous acid

– HClO2: chlorous acid

Acid Nomenclature

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

• change the ending to -ic acid.

___________ic acid

– HClO3: chloric acid

I

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

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.

Follow the octet rule

except for hydrogen, which only needs two electrons to be full

Connect the electrons as lines

Keep track of the electrons:

26 - 6 = 20

Writing Lewis Structures

3. Fill the octets of the outer atoms.

Keep track of the electrons:

26 - 6 = 20; 20 - 18 = 2

Writing Lewis Structures

4. Fill the octet of the central atom.

5. Finish by checking for octets.

Keep track of the electrons:

26 - 6 = 20; 20 - 18 = 2; 2 - 2 = 0

Writing Lewis Structures

6. If you run out of electrons before the central atom has an octet…

…form multiple bonds until it does.

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-