How to Draw Bohr Diagrams

Classroom Norms

• Be Respectful
• Give other students an opportunity to learn by being quiet
• Be Responsible
• Take notes and do assignments when asked
• Be Safe
• Refrain from throwing things in class
• Only have water in a sealable container
• Any others you feel are important

Setting up our notebook

• Page 11
• Topic: Bohr model
• Essential question: How do I draw a Bohr model?
• Quick write: What were some of the previous models of the atom and why were they not good enough.

Atomic Structure

• Atoms have a nucleus that contains Protons and Neutrons
• Electrons are contained in shells that surround the nucleus
• An atom is made of mostly empty space

Valence Electrons

• Each electron shell can hold a certain number of electrons
• Electron shells are filled from the inside out
• Noble Gases (last column) have full outer electron shells
• All other elements have partially filled outer electron shells

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We will only

look at these

Valence Electrons

• The electrons in the outer most electron shell are called valence electrons
• The shell containing electrons that is furthest from the nucleus is called the valence shell
• The number of electron shells with electrons is the same as (=) the period number
• Atoms will try to gain or lose electrons to have a full valence shell
• Valence electrons are the electrons that interact with other atoms… = chemistry!

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Bohr Diagrams

• Find your element on the periodic table.
• Determine the number of electrons – it is the same as the atomic number.
• This is how many electrons you will draw.

Bohr Diagrams

• Find out which period (row) your element is in.
• Elements in the 1^st period have one energy level.
• Elements in the 2^nd period have two energy levels, and so on.

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Bohr Diagrams

• Draw a nucleus –place a P and an N in the inside circle to represent Protons and Neutrons.
• Carbon is in the 2^nd period, so it has two energy levels, or shells.
• Draw the shells around the nucleus.

P =

N =

Bohr Diagrams

• Add the electrons.
• Carbon has 6 electrons.
• The first shell can only hold 2 electrons.

P = 6

N = 6

Bohr Diagrams

• Since you have 2 electrons already drawn, you need to add 4 more.
• These go in the 2^nd shell.
• Add one at a time -starting on the right side and going counter clock-wise.

P = 6

N = 6

Bohr Diagrams

• Check your work.
• You should have 6 total electrons for Carbon.
• Only two electrons can fit in the 1^st shell.
• The 2^nd shell can hold up to 8 electrons.

P = 6

N = 6

You try

• Draw the Bohr model for Oxygen

• Draw the Bohr model for Lithium

P =

N =

P =

N =

Bohr Diagrams

You should know how to draw a Bohr Diagram for the first 20 elements.

On page 12 make the following table and choose an element from each of the first three rows of the periodic table to complete the table

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What can the periodic table tell us?

• Opposites __________
• An electron stays around the nucleus because of the attraction to ______________
• Draw a Bohr model for Li, Na, K and answer the following questions:

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1. What is the main difference in the Bohr models?

2. Which element do you think could lose its electron easier? Hint: which element may have the weakest attraction between electron and proton

3. Is an element more or less reactive if it can lose a valence electron easier?

4. Which element is more reactive?

5. What does this tell you about the trend in periodic table?

What can the periodic table tell us?

• The PERIOD (row) tells us how many ____________an atom has. All elements in a period have the same number of energy levels.

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• The number of valence electrons _________ as we move up in family (column)

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• The reactivity of an element _________ as we move down the table, because__________________________________________________

Closing on notes on Pg 11.

• Circle key terms

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• Underline key themes

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• At least 3 level 1 questions, 2 level 2 questions, and 1 level 1 question.

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• Summary (answers essential question)