# C4 - Electron Shells

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• Created on: 17-02-16 18:18

ELECTRON SHELLS

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## Electron Shells

Electron Shells:

• Electrons always occupy shells
• Lowest shells are always filled first
• In the 1st Shell there is 2,  2nd Shell there is 8, 3rd Shell there is 8
• Atoms are happier when they have full electrons
• In most atoms the outer shell is not full and this makes the atom want to react

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## Electron Configuration

How to work out the electron configurations:

• Find the element in the periodic table and circle the proton number
• eg. Nitrogen has a proton number of 7
• 2. Whatever the number of protons is,the number of electrons is the same
• eg. Nitrogen has 7 protons so it must have 7 electrons
• 3. Follow the electron shell rules. The first shell can only take 2 electrons and the second shell can take a maximum of 8 electrons
• So the electron configuration for nitrogen must be 2 , 5 ( 2 + 5 = 8 )

Example (Argon)

• Proton number of 18
• 2 in the first shell, 8 in the second shell and then there has to be 8 in the 3rd as well
• 2 , 8, 8  (2+8+8=18)
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