The Bohr Model

Recall the structure of the atom

Recall the structure of the atom Electron Shells Neutron Nucleus Proton Valence shell

Recall the structure of the atom Electron Shells Neutron Nucleus Proton Valence shell Sometimes, we need to represent atoms in a simplified way

Bohr Diagrams

Bohr Diagrams Bohr diagrams are a simplified way to represent atoms

Bohr Diagrams Bohr diagrams are a simplified way to represent atoms The key features of a Bohr diagram are:

Bohr Diagrams Bohr diagrams are a simplified way to represent atoms The key features of a Bohr diagram are: Electron shells

Bohr Diagrams Bohr diagrams are a simplified way to represent atoms The key features of a Bohr diagram are: Electron shells Electron placement within the shells

Bohr Diagrams Bohr diagrams are a simplified way to represent atoms The key features of a Bohr diagram are: Electron shells Electron placement within the shells A simplified nucleus to show what element it is (this can be done in different ways)

Bohr Diagrams Bohr diagrams are a simplified way to represent atoms The key features of a Bohr diagram are: Electron shells Electron placement within the shells A simplified nucleus to show what element it is (this can be done in different ways)

Bohr Diagrams Bohr diagrams are a simplified way to represent atoms The key features of a Bohr diagram are: Electron shells Electron placement within the shells A simplified nucleus to show what element it is (this can be done in different ways)

Bohr Diagrams Bohr diagrams are a simplified way to represent atoms The key features of a Bohr diagram are: Electron shells Electron placement within the shells A simplified nucleus to show what element it is (this can be done in different ways) The primary purpose of a Bohr diagram is to show electron placement

Electrons Electrons are not randomly dispersed amongst the electron shells

Electrons Electrons are not randomly dispersed amongst the electron shells Each electron shell can only hold a specific number of electrons

Electrons Electrons are not randomly dispersed amongst the electron shells Each electron shell can only hold a specific number of electrons First shell: up to two electrons

Electrons Electrons are not randomly dispersed amongst the electron shells Each electron shell can only hold a specific number of electrons First shell: up to two electrons Second shell: up to eight electrons

Electrons Electrons are not randomly dispersed amongst the electron shells Each electron shell can only hold a specific number of electrons First shell: up to two electrons Second shell: up to eight electrons Third shell: up to eight electrons

Electrons Electrons are not randomly dispersed amongst the electron shells Each electron shell can only hold a specific number of electrons First shell: up to two electrons Second shell: up to eight electrons Third shell: up to eight electrons Fourth shell: up to eighteen electrons

Electrons Electrons are not randomly dispersed amongst the electron shells Each electron shell can only hold a specific number of electrons First shell: up to two electrons Second shell: up to eight electrons Third shell: up to eight electrons Fourth shell: up to eighteen electrons Etc. (there are more shells but we will deal with just the first four)

Electrons Electrons are not randomly dispersed amongst the electron shells Each electron shell can only hold a specific number of electrons First shell: up to two electrons Second shell: up to eight electrons Third shell: up to eight electrons Fourth shell: up to eighteen electrons Etc. (there are more shells but we will deal with just the first four) The electron shells fill in a specific order

Electrons Electrons are not randomly dispersed amongst the electron shells Each electron shell can only hold a specific number of electrons First shell: up to two electrons Second shell: up to eight electrons Third shell: up to eight electrons Fourth shell: up to eighteen electrons Etc. (there are more shells but we will deal with just the first four) The electron shells fill in a specific order The first shell must be filled before any electrons can enter the second shell

Electrons Electrons are not randomly dispersed amongst the electron shells Each electron shell can only hold a specific number of electrons First shell: up to two electrons Second shell: up to eight electrons Third shell: up to eight electrons Fourth shell: up to eighteen electrons Etc. (there are more shells but we will deal with just the first four) The electron shells fill in a specific order The first shell must be filled before any electrons can enter the second shell The second shell must be filled before any electrons can enter the third shell

Electrons Electrons are not randomly dispersed amongst the electron shells Each electron shell can only hold a specific number of electrons First shell: up to two electrons Second shell: up to eight electrons Third shell: up to eight electrons Fourth shell: up to eighteen electrons Etc. (there are more shells but we will deal with just the first four) The electron shells fill in a specific order The first shell must be filled before any electrons can enter the second shell The second shell must be filled before any electrons can enter the third shell Etc.

Electrons Electrons are not randomly dispersed amongst the electron shells Each electron shell can only hold a specific number of electrons First shell: up to two electrons Second shell: up to eight electrons Third shell: up to eight electrons Fourth shell: up to eighteen electrons Etc. (there are more shells but we will deal with just the first four) The electron shells fill in a specific order The first shell must be filled before any electrons can enter the second shell The second shell must be filled before any electrons can enter the third shell Etc. The only electron shell that can be partially filled is the valence shell

Example: Carbon

Example: Carbon Carbon has: 6 protons 6 electrons

Example: Carbon Carbon has: 6 protons 6 electrons Recall: in order to be neutral, an atom must have the same number of protons as electrons 6 +1 +6 −1 =0 Assume atoms are neutral unless specified otherwise (more to come next lesson)

Example: Carbon Carbon has: 6 protons 6 electrons Draw nucleus

Example: Carbon Carbon has: Draw nucleus 6 protons 6 electrons Draw nucleus Label number of protons 6 𝑝 +

Example: Carbon Carbon has: Draw nucleus Draw first electron shell 6 protons 6 electrons Draw nucleus Label number of protons Draw first electron shell 6 𝑝 +

Example: Carbon Carbon has: Draw nucleus Draw first electron shell 6 protons 6 electrons Draw nucleus Label number of protons Draw first electron shell Fill first electron shell Can contain up to two electrons 6 𝑝 +

Example: Carbon Carbon has: Draw nucleus Draw first electron shell 6 protons 6 electrons Draw nucleus Label number of protons Draw first electron shell Fill first electron shell Can contain up to two electrons 6 – 2 = 4 electrons, we still need to draw four more electrons 6 𝑝 +

Example: Carbon Carbon has: Draw nucleus Draw first electron shell 6 protons 6 electrons Draw nucleus Label number of protons Draw first electron shell Fill first electron shell Can contain up to two electrons 6 – 2 = 4 electrons, we still need to draw four more electrons Draw second shell 6 𝑝 +

Example: Carbon Carbon has: Draw nucleus Draw first electron shell 6 protons 6 electrons Draw nucleus Label number of protons Draw first electron shell Fill first electron shell Can contain up to two electrons 6 – 2 = 4 electrons, we still need to draw four more electrons Draw second shell Place final four electrons in shell 6 𝑝 +

Example: Magnesium

Example: Magnesium Magnesium has: 12 protons 12 electrons

Example: Magnesium Magnesium has: 12 protons 12 electrons Draw nucleus

Example: Magnesium Magnesium has: Draw nucleus 12 protons 12 electrons Draw nucleus Label number of protons 12 𝑝 +

Example: Magnesium Magnesium has: Draw nucleus 12 protons 12 electrons Draw nucleus Label number of protons Draw first electron shell 12 𝑝 +

Example: Magnesium Magnesium has: Draw nucleus 12 protons 12 electrons Draw nucleus Label number of protons Draw first electron shell Fill first electron shell Can contain up to two electrons 12 𝑝 +

Example: Magnesium Magnesium has: Draw nucleus 12 protons 12 electrons Draw nucleus Label number of protons Draw first electron shell Fill first electron shell Can contain up to two electrons 12 – 2 = 10 electrons, we still need to draw ten more electrons 12 𝑝 +

Example: Magnesium Magnesium has: Draw nucleus 12 protons 12 electrons Draw nucleus Label number of protons Draw first electron shell Fill first electron shell Can contain up to two electrons 12 – 2 = 10 electrons, we still need to draw ten more electrons Draw second shell 12 𝑝 +

Example: Magnesium Magnesium has: Draw nucleus 12 protons 12 electrons Draw nucleus Label number of protons Draw first electron shell Fill first electron shell Can contain up to two electrons 12 – 2 = 10 electrons, we still need to draw ten more electrons Draw second shell Fill second electron shell Can contain up to eight electrons 12 𝑝 +

Example: Magnesium Magnesium has: Draw nucleus 12 protons 12 electrons Draw nucleus Label number of protons Draw first electron shell Fill first electron shell Can contain up to two electrons 12 – 2 = 10 electrons, we still need to draw ten more electrons Draw second shell Fill second electron shell Can contain up to eight electrons 10 – 8 = 2 electrons, we still need to draw two more electrons 12 𝑝 +

Example: Magnesium Magnesium has: Draw nucleus 12 protons 12 electrons Draw nucleus Label number of protons Draw first electron shell Fill first electron shell Can contain up to two electrons 12 – 2 = 10 electrons, we still need to draw ten more electrons Draw second shell Fill second electron shell Can contain up to eight electrons 10 – 8 = 2 electrons, we still need to draw two more electrons Draw third shell 12 𝑝 +

Example: Magnesium Magnesium has: Draw nucleus 12 protons 12 electrons Draw nucleus Label number of protons Draw first electron shell Fill first electron shell Can contain up to two electrons 12 – 2 = 10 electrons, we still need to draw ten more electrons Draw second shell Fill second electron shell Can contain up to eight electrons 10 – 8 = 2 electrons, we still need to draw two more electrons Draw third shell Place remaining two electrons in shell 12 𝑝 +

Practice Time!!!

Draw the following Bohr diagrams

Draw the following Bohr diagrams Hydrogen Phosphorous

Draw the following Bohr diagrams Hydrogen Phosphorous 1 𝑝 +

Draw the following Bohr diagrams Hydrogen Phosphorous 1 𝑝 + 15 𝑝 +

What element is represented by the Bohr diagram?

What element is represented by the Bohr diagram?

What element is represented by the Bohr diagram? Answer: Neon

What element is represented by the Bohr diagram? Answer: Neon

What element is represented by the Bohr diagram? Answer: Sodium Answer: Neon

What element is represented in the following Bohr diagrams

What element is represented in the following Bohr diagrams

What element is represented in the following Bohr diagrams Answer: oxygen There are 8 electrons Must have 8 protons Must be oxygen

What element is represented in the following Bohr diagrams Answer: oxygen There are 8 electrons Must have 8 protons Must be oxygen ?

What element is represented in the following Bohr diagrams Answer: oxygen There are 8 electrons Must have 8 protons Must be oxygen Answer: argon There are 18 electrons Must have 18 protons Must be argon ?

How many shells would the following elements have?

How many shells would the following elements have? Lithium

How many shells would the following elements have? Lithium Answer: 2 Lithium has 3 protons Must have 3 electrons First shell: 2 Second shell: 1

How many shells would the following elements have? Lithium Answer: 2 Lithium has 3 protons Must have 3 electrons First shell: 2 Second shell: 1 Calcium

How many shells would the following elements have? Lithium Answer: 2 Lithium has 3 protons Must have 3 electrons First shell: 2 Second shell: 1 Calcium Answer: 4 calcium has 20 protons Must have 20 electrons First shell: 2 Second shell: 8 Third shell: 8 Fourth shell: 2