Today you need:
12/14
‐paper
‐notes
‐periodic table
‐covalent compound worksheet
Warm UP: Copy the Following onto a seperate sheet of paper:
Material covered on the Exam:
‐intro to atomic theory (ch 5 and 17)
‐how to use the periodic table
‐vocabulary on elements, compounds and mixtures (ch 16)
‐physical and chemical changes (ch 2)
‐balancing equations
‐types of reactions (synthesis, replacement, and decomposition)
‐ionization
‐naming compounds both ionic and covalent
‐Lewis Structures
Today we will:
‐Discuss Covalent compounds‐ Polar and non‐polar compounds
‐Practice with naming covalent compounds
‐Review for Exam
Title: Dec 14­6:52 AM (1 of 15)
Forming Covalent Bonds:
• Covalent Bonds form when 2 elements SHARE electrons on the outer shell (valence electrons)
• Both atoms sharing the electrons attract the electrons equally
• Can form more than one bond‐ can make double or triple bonds!
• Lewis DOT structures help!‐ shared pairs of electrons count for each atom that is sharing them
Properties: • MUCH lower melting and boiling point than Ionic Compounds‐ Forces holding covalent bonds together are much weaker than ionic bonds so... .... Less heat required to separate the particles than in an ionic solid.
• Very poor conductors of electricity‐ no charged particles move around in covalent solids and so...
... no charged particles to help electricity move ***That is why molecular soilds like plastic are used as electrical insulators!!***
Title: Dec 14­7:12 AM (2 of 15)
Title: Dec 14­7:12 AM (3 of 15)
Unequal Sharing of Electrons:
• Some atoms pull on shared electrons harder than other atoms so...
... the shared electrons move a little closer to toward one atom than another RESULT: one part of the molecule has a slight + charge another part has a slight ‐ charge called a POLAR molecule‐ not as strong as an ion, but definitely different charges in different parts of the molecule.
Two Atoms that pull on shared electrons equally‐ neither atom is charged and the NON‐POLAR molecule is referred to as Example: Carbon Dioxide (CO 2)
POLAR MOLECULE:
Water is polar. Oxygen pulls harder on the shared electrons and so the shared electrons spend more time around the oxygen end than the hydrogen end. RESULT: The oxygen side is slightly negative, the hydrogen side is slightly positive
Title: Dec 14­7:13 AM (4 of 15)
Naming Covalent Compounds
Several methods or systems for naming chemicals have been developed over the years.
Simple names are used for ionic compounds (and some covalent compounds) where only one compound is made from those elements.
Latin names are used for ionic compounds (and some covalent compounds) where more than one compound is made from those elements.
Stock names are used for ionic compounds and covalent compounds where more than one compound is made from those elements. Prefix names are used for covalent compounds. Title: Dec 14­7:13 AM (5 of 15)
Using Prefixes to name Covalent Compounds
Covalent compounds are named in different ways than ionic compounds (although there is some overlap). Many of these compounds have common names such as "methane", "ammonia" and "water". However, simple covalent compounds are generally named by using prefixes to indicate how many atoms of each element are shown in the formula. Also, the ending of the last (most negative) element is changed to ‐ide.
The prefixes used are mono‐, di‐, tri‐, tetra‐, penta‐, hexa‐, and so forth. The mono‐ prefix is usually not used for the first element in the formula. The "o" and "a" endings of these prefixes commonly are dropped when they are attached to "oxide." You should memorize the prefixes from 1‐10
1
2
3
4
5
6
7
8
9
10
mono‐
di‐
tri‐
tetra‐
penta‐
hexa‐
Hepta‐
octa‐
nona‐
deca‐
You also need to know which element to put first in the formulas!
Generally, they are in the same left‐to‐right order that they are on the periodic table, except that you would have to squeeze hydrogen in between nitrogen and oxygen.
Title: Dec 14­7:14 AM (6 of 15)
Name the following compounds.
PH3
N2O3
CO
SO2
HI
SCl6
CH4
NH3
H2O
HCl
Title: Dec 14­7:14 AM (7 of 15)
phosphorus trihydride
dinitrogen trioxide
carbon monoxide
sulfur dioxide
hydrogen monoiodide*
sulfur hexachloride
methane carbon tetrahydride
ammonia nitrogen trihydride
water
dihydrogen monoxide
On you own paper draw the Lewis structures for the following:
use different colors to represent electrons from different elements
CH4
BH3
H2O
CO2
O3
CH3OH
Title: Dec 14­7:16 AM (8 of 15)
Title: Dec 14­7:03 AM (9 of 15)
Title: Dec 14­7:08 AM (10 of 15)
Title: Dec 14­7:06 AM (11 of 15)
Today you need:
‐paper
‐notes
‐periodic table
Warm UP: 38 +2
Sr
87
Today we will:
‐Review for Exam
Title: Dec 14­6:52 AM (12 of 15)
12/15
How many: protons?, electrons? neutrons?, draw the Lewis Structure‐ Whats the name?
Title: Dec 15­7:34 AM (13 of 15)
Title: Dec 15­9:28 AM (14 of 15)
Title: Dec 15­7:34 AM (15 of 15)