Both are valuable in a different way!

Bohr Model & Lewis Dot Diagrams

Recall...

There are two models of the atoms we will be using in class.

Bohr ModelLewis Dot Structure

Bohr ModelThe Bohr Model shows all of the particles in

the atom.In the center is circles. Each circle

represents a single neutron or proton. Protons should have a plus or P written on them. Neutrons should be blank or have an N.

In a circle around the nucleus are the electrons. Electrons should have a minus sign or an e.

You can’t just shove all of the electrons into the first orbit of an electron.

Electrons live in something called shells or energy levels.

Only so many can be in any certain shell. The electrons in the outer most shell of any

element are called valance electrons.

Draw a Bohr Model for LithiumDrawing a Lithium atom

1. look at the Periodic Tabledetermine the number of protons & neutrons

(protons = the atomic number)(neutrons = Atomic mass minus number of protons)

determine the number of electrons(electrons match the number of protons for neutral atoms)

2. add protons, neutrons and electrons to their proper positions

Try drawing a Bohr Model for the following elements:

a) Hb) Hec) O

Bohr Diagrams can become crowded!

Lewis Dot DiagramsThe Lewis Dot Structure is a bit different

from the Bohr model. It only shows the element symbol and it’s

outer most electron shell.

Step 1: Write the Element Symbol

Step 2: Find the number of electrons in the outermost energy level of the Bohr Model (Valence Electrons)

Step 3: Place the electrons (dots) around the symbol in clockwise order so that there are no more than 2 electrons per side.

Lewis Diagrams solve the “crowding” problem

SummaryBohr models are good because they show

the energy level of all electrons in an atom.

Lewis models are good because they eliminate the “crowded’ picture for elements with many subatomic particles (protons, neutrons, and electrons)

Presentation QuizTry drawing a Bohr Model for the following elements:

a) Hb) Hec) O

Try drawing a Lewis Model for those elements:

d) He) Hef) O