chapter 6 -covalent compounds section 2 - drawing and naming molecules
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Chapter 6 -Covalent compounds Section 2 - Drawing and Naming Molecules. Chapter 6 -Covalent compounds Section 2 - Drawing and Naming Molecules. Lewis Electron-Dot Structures. In 1920,G.N. Lewis, the American chemist came up with a system to represent - PowerPoint PPT PresentationTRANSCRIPT
Chapter 6 -Covalent compoundsSection 2 - Drawing and Naming Molecules
Chapter 6 -Covalent compoundsSection 2 - Drawing and Naming Molecules
Lewis Electron-Dot Structures
In 1920,G.N. Lewis, the American chemist came up with a system to represent the valence electrons of an atom. This system - known as electron-dot diagramsor Lewis structures - uses dots to represent valence electrons. Lewis’s systemis a valuable model for covalent bonding.
A Lewis structure shows only the valence electrons in an atom or molecule.The nuclei and the electrons of the inner energy levels (if any) of an atomare represented by the symbol of the element.
Chapter 6 -Covalent compoundsSection 2 - Drawing and Naming Molecules
Group # # Valence e- Electron Dot Structure(example)
1
2
13
14
15
16
17
18
1
2
3
4
5
6
7
8
Chapter 6 -Covalent compoundsSection 2 - Drawing and Naming Molecules
Rules for Electron Dot Structures1. Each atoms is drawn with its symbol surrounded by one dot for each of its valence numbers. No more than 2 dots to a side.
2. Determine if you are drawing an ionic or covalent substance.
Ionic – Must show the charges due to lose/gain of electron(s), anionsare to be placed in brackets [ X]2-
Covalent – Must show the shared pair(s) of electrons
3. No more than 8 electrons around any atom.(H, He, B, and Be will only have 2)
4. Covalent may have up to 3 bonds between atoms.
Chapter 6 -Covalent compoundsSection 2 - Drawing and Naming Molecules
Draw dot structures for CH4
Chapter 6 -Covalent compoundsSection 2 - Drawing and Naming Molecules
Draw dot structures for NaCl
Chapter 6 -Covalent compoundsSection 2 - Drawing and Naming Molecules
Draw dot structures for H2O
Chapter 6 -Covalent compoundsSection 2 - Drawing and Naming Molecules
Draw dot structures for NH4+
Chapter 6 -Covalent compoundsSection 2 - Drawing and Naming Molecules
Draw dot structures for CaSO4
Chapter 6 -Covalent compoundsSection 2 - Drawing and Naming Molecules
Draw dot structures for MgCl2
Chapter 6 -Covalent compoundsSection 2 - Drawing and Naming Molecules
Draw dot structures for CO2
Chapter 6 -Covalent compoundsSection 2 - Drawing and Naming Molecules
Draw dot structures for F2
Chapter 6 -Covalent compoundsSection 2 - Drawing and Naming Molecules
Naming Covalent Compounds
Covalent compounds made of two elements are named by using amethod similar to the one used to name ionic compounds.
Covalent Compounds usually list the most electronegative element last.This element will have the “–ide” ending that is usually found on ions.
The first element listed will keep its periodic table name.
For example, SO2
The first element keeps its periodic name -- Sulfur
The last element picks up the “–ide” ending -- Oxide
Chapter 6 -Covalent compoundsSection 2 - Drawing and Naming Molecules
Prefixes Indicate How Many Atoms Are in a MoleculePrefixes are used to tell how many of each element are found in each molecule. A prefix is added to the name of the first element and one is added to the second element.
Prefix Number
Prefix Number
1 6
2 7
3 8
4 9
5 10
Mono
Di
Tri
Tetra
Penta
Hexa
Hepta
Octa
Nona
Deca
Chapter 6 -Covalent compoundsSection 2 - Drawing and Naming Molecules
Prefixes are not used on the first element if there is only one of them.
SO2
SO3
P4O6
Nitrogen Dioxide
Carbon Monoxide
Dinitrogen Tetraoxide
Sulfur Dioxide
Sulfur Trioxide
Tetraphosphorus Hexaoxide
NO2
CO
N2O4
The diatomic 7There are seven molecules that commonly bond with themselves andform a diatomic molecule (molecule with two atoms). These moleculesare never found in nature as atoms, only in their diatomic form. They will keep their atomic name.
Hydrogen H2
Nitrogen N2
Oxygen O2
Fluorine F2
Chlorine Cl2Bromine Br2
Iodine I2
Chapter 6 -Covalent compoundsSection 2 - Drawing and Naming Molecules
Review
Which is the correct electron-dot formula for a molecule of chlorine?
Which electron-dot diagram best represents a compound that contains both ionic and covalent bonds?
Chapter 6 -Covalent compoundsSection 2 - Drawing and Naming Molecules
Review
Which molecule contains a polar covalent bond?
What is the correct Lewis electron-dot structure for the compound magnesium fluoride?
Chapter 6 -Covalent compoundsSection 2 - Drawing and Naming Molecules
Review
Which diagram below shows the correct Lewis electron-dot diagramfor a molecule of phosphorus trichloride, PCl3?
Which Lewis electron-dot diagram is correct for CO2?
Chapter 6 -Covalent compoundsSection 2 - Drawing and Naming Molecules
Review
What is the IUPAC name for P2O5?1. Phosphorus Oxide2. Diphosphorus Pentaoxygen3. Diphosphorus Oxide4. Diphosphorus Pentaoxide
What is the formula for Nitrogen Disulfide?1. NS2. N2S3. NS2
4. N2S2
Chapter 6 -Covalent compoundsSection 2 - Drawing and Naming Molecules
Review
Chapter 6 -Covalent compoundsSection 2 - Drawing and Naming Molecules
Review