Valence Electrons &

Bohr Diagrams

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

• Protons have a positive charge

• Electrons have a negative charge

• Neutrons are Neutral

Valence Electrons

• Each electron shell can hold a certain number of electrons

• Electron shells are filled from the inside out

• Noble Gases have full outer electron shells

• All other elements have partially filled outer electron shells

Electron Shell

Number of Electrons

1 2

2 8

3 8

4 18

5 18

6 32

7 32

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

Noble Gas Stability

• Noble gases are usually unreactive• This is because they have full valence

shells• An element with a full valence shell is a

happy element • For two atoms to join together atoms must

gain, lose or share electrons• Elements with full valence shells do not

easily gain or lose electrons

Noble Gas Stability

• Atoms want to gain stability

• Atoms will try to gain or lose electrons to have a full valence shell

• Metals try to lose electrons

• Non-Metals try to gain electrons

Becoming An Ion

• Electrons are negatively charged

• Protons are positively charged

• Neutral atoms do not have a charge because the number of protons is the same as the number of electrons

• When atoms gain or lose electrons they become positively or negatively charged

• An atom with a charge is called an Ion

Bohr Models

• Niels Bohr created a visual model of the atom to make them easy to understand

• A Bohr Model contains a central nucleus surrounded by electron shells

• For each model you state the number of protons and neutrons in the nucleus and draw a dot on the electron shells for each electron