Post on 18-Jan-2018
description
◦ Name Color Burned 1 2 3 4 5 6 Unknown #1 Unknown #2
Today’s Lab
Modeling and Representing Atoms on Paper
How to draw Bohr Diagrams and Electron Dot Diagrams (sometimes called Lewis
Structures)
Pictographic representation of an Atom Shows information about the nucleus Electron energy levels Good for index cards and flash cards
Bohr Diagrams
Start with a rectangle about 2” x 4”
Bohr Diagrams
At the top write the name, Atomic number, Mass number of the element and the atomic mass
Bohr Diagrams
Carbon Atomic # = 6 Mass # = 12
Atomic mass = 12.011 amu
Draw a small circle below the text that will represent the nucleus of the atom
Bohr Diagrams
In the circle write: the elemental symbol the number of Protons the number of Neutrons
Carbon Atomic # = 6 Mass # = 12
Atomic mass = 12.011 amu
C 6p+
6n0
Draw a larger circle around the nucleus circle to represent the first energy level for electrons
Bohr Diagrams
Carbon Atomic # = 6 Mass # = 12
Atomic mass = 12.011 amu
Add more circles outside to include all of the energy levels you need for the atom.
(Hint: In what period is the element?)
Carbon is in Period two and therefore needs two energy levels
C 6p+
6n0
Find out which period (row) your element is in.
Elements in the 1st period have one energy level.
Elements in the 2nd period have two energy levels, and so on.
Bohr Diagrams
Now add electrons, as small dots, to each energy level as allowed until you have the proper number of electrons for a neutral element.
Bohr Diagrams
Carbon Atomic # = 6 Mass # = 12
Atomic mass = 12.011 amuThe number of electrons should be equal to the number of protons.
Remember:Energy Level
# of e-
1 22 83 8
C 6p+
6n0
If you need a third level make your circles a little smaller.
You now have a complete Bohr Diagram
Bohr Diagrams
Carbon Atomic # = 6 Mass # = 12
Atomic mass = 12.011 amu
C 6p+
6n0
1) Draw a nucleus with the element symbol inside.
2) Carbon is in the 2nd period, so it has two energy levels, or shells.
3) Draw the shells around the nucleus.
Bohr Diagrams
C
1) Add the electrons.2) Carbon has 6
electrons.3) The first shell can
only hold 2 electrons.
Bohr Diagrams
C
1) Since you have 2 electrons already drawn, you need to add 4 more.
2) These go in the 2nd shell.
3) Add one at a time -starting on the right side and going counter clock-wise.
Bohr Diagrams
C
1) Check your work.2) You should have 6
total electrons for Carbon.
3) Only two electrons can fit in the 1st shell.
4) The 2nd shell can hold up to 8 electrons.
5) The 3rd shell can hold 18, but the elements in the first few periods only use 8 electrons.
Bohr Diagrams
C
Try the following elements on your own:
a) Hb) Hec) Od) Ale) Nef) K
Bohr Diagrams
C
Try the following elements on your own:
a) H – 1 electronb) Hec) Od) Ale) Nef) K
Bohr Diagrams
H
Try the following elements on your own:
a) Hb) He - 2 electronsc) Od) Ale) Nef) K
Bohr Diagrams
He
Try the following elements on your own:
a) Hb) Hec) O - 8 electronsd) Ale) Nef) K
Bohr Diagrams
O
Try the following elements on your own:
a) Hb) Hec) Od) Al - 13 electronse) Nef) K
Bohr Diagrams
Al
Try the following elements on your own:
a) Hb) Hec) Od) Ale) Ne - 10 electronsf) K
Bohr Diagrams
Ne
Try the following elements on your own:
a) Hb) Hec) Od) Ale) Nef) K - 19 electrons
Bohr Diagrams
K
Also called Lewis Structures Representation of valence electrons only Useful only for “Representative elements” Gives some indication of the geometry
(shape) of compounds when used for bonding diagrams
Easy to draw
Electron Dot Diagrams
To find the # of valence electrons look at the group
Group 1 Group 2 Group # = # of valence electrons
Valence Electrons
The Elemental Symbol serves as the representation of the nucleus
Electron Dot Diagrams
Dots are added around the nucleus to show electrons only in the outer energy level
Electron Dot Diagrams
Carbon has only 4 electrons in the 2nd energy level so we need only represent those 4
Like the Hund rule add 1 electron per side, then add more as needed.
Lewis structures only apply to “Representative elements” (Group A elements)
Electron Dot Diagrams
Only s and p sublevel electrons in the outer or highest energy level are shown. These are called valence electrons.
The maximum number of electrons that can be shown are 8
Lewis structures only apply to “Representative elements” (Group A elements)
Electron Dot Diagrams
The maximum number of electrons that can be shown are 8
Only s and p sublevel electrons in the outer or highest energy level are shown. These are called valence electrons.
Lewis structures only apply to “Representative elements” (Group A elements)
Electron Dot Diagrams
The maximum number of electrons that can be shown are 8
Only s and p sublevel electrons in the outer or highest energy level are shown. These are called valence electrons.
Lewis structures only apply to “Representative elements” (Group A elements)
Electron Dot Diagrams
The maximum number of electrons that can be shown are 8
Only s and p sublevel electrons in the outer or highest energy level are shown. These are called valence electrons.
Transition metals don’t have valence electrons. They have Oxidation Numbers
Electron Dot Diagrams
+2 +2 +2 +4
We’ll Talk about Oxidation Numbers Next Week!