Chemistry Brooks Homework/Notes

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CHAPTER 8 NOTES

Covalent bond

Þ    Sharing of electrons

Þ    Most are formed between two non-metals

Because non-metals have close (higher) electronegativity… to get stable.. they share the electrons. One electron will help another become stable.

Þ    Covalent Bonds are sometimes called molecular compounds:

1.      They normally have low melting and boiling points (Many are gases are liquid at room temperature or huge liquids)

2.      They are individual… not in large matrix’s

3.      They are incredibly useful

·       Any unpaired electron can form a covalent bond

·       The number of unpaired electrons will determine the number of covalent bonds formed.

Diatomic Elements:

Þ    Molecules when found in nature... have two atoms.

Þ    Will have a ₂ subscript

Þ    2 electrons that are shared are going to form a bond (covalent bond) They will share enough electrons to get to 8 electrons (STABLE)

Þ    Even sharing of electrons, p sub-levels will overlap

Þ    Example: Fluorine F₂ (has 7 valence electrons) It can form one covalent bond because it only has one unpaired electron.

Þ    Examples: All Halogens are diatomic

1.      Nitrogen

2.      Oxygen

3.      Fluorine

4.      Chlorine

5.      Bromine

6.      Iodine

7.      Hydrogen

OCTET: 8 = STABLE

VALENCE ELECTRONS: The number of electrons in the Outer most level

Lewis Structure for Molecules

1.     Draw the Lewis Structure for each element in the molecule

2.     Determine the total number of valence electrons for the molecule

3.     Determine the center atoms and draw its Lewis Structure

4.     Pair the atoms attached to the center atom based on the unpaired electrons.

5.     Check accuracy by for the LEWIS STRUCTURE

1)    There should be no unpaired electrons

2)    Counting the total valance electrons

3)    Making sure that each atom (except hydrogen) follow the octet rule.

Centric Molecule: Will have a center atom that will be surrounded by other atoms.

EXAMPLE:

PH³

1. Number of Valence Electrons

P             H³

5 (ve)   1(ve) x 3   =   8 (ve)  VALENCE ELECTRONS

2. Determine the center atom (highest unpaired electrons)

                        P

HOW TO DETERMINE THE CENTER ATOM:

·      The one with the most unpaired electrons

·      Lowest eletron negativity

·      The One written first

HOMEWORK:

1.     PH₃

2.     H₂S

3.     HCl

4.     CCl₄

5.     SiH₄

_{ALSO PICK UP YOUR MAKEUP WORK FROM MRS> FERRELL AFTER SCHOOL. IT IS DUE BEFORE SCHOOL TOMORROW.}