# Electron Shells and Elements

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How many electrons are allowed in each electron shell?
2,8,8,2
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What is the electronic configuration for nitrogen (it has seven protons)
protons = electrons, so nitrogen has seven electrons that are contained in it's energy shells. This means that there must be two electrons in the lowest energy level (the one nearest to the nucleus) and 5 in the second shell so EC = 2,5.
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What is the electronic configuration of chlorine? (17 protons)
2.8.7.
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What is the electronic configuration of calcium? (20 protons)
2.8.8.2.
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How many types of atoms do elements consist of?
They consist of one type of atom only.
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Each element has..
A different number of protons - it's the number of protons in an atom that decides what element it is.
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What does the atomic number tell you about an atom?
The atomic number is on the bottom and tells you how many protons there are in an atom (so therefore also the number of electrons)
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What does the mass number tell you about an atom?
The mass number is on the top and tells how many protons + neutrons there are in the atom.
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How can you find out how many neutrons there are in an atom by using an atoms mass and atom number?
mass number = protons + neutrons and atomic number = protons, so just subtract the atomic number from the mass number and it will give you the amount of neutrons.
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## Other cards in this set

### Card 2

#### Front

What is the electronic configuration for nitrogen (it has seven protons)

#### Back

protons = electrons, so nitrogen has seven electrons that are contained in it's energy shells. This means that there must be two electrons in the lowest energy level (the one nearest to the nucleus) and 5 in the second shell so EC = 2,5.

### Card 3

#### Front

What is the electronic configuration of chlorine? (17 protons)

### Card 4

#### Front

What is the electronic configuration of calcium? (20 protons)

### Card 5

#### Front

How many types of atoms do elements consist of?