3.4 How electrons are arranged Flashcards
Electron shells
Electrons are arranged in shells around the nucleus.
The first shell, closest to the nucleus, is the lowest energy level.
The further a shell is from the nucleus, the higher the energy level.
How many electrons can the first shell hold?
The first shell can only hold 2 electrons. It fills first.
How many electrons can the second shell hold?
The second shell holds 8 electrons.
How many electrons can the third and fourth shell hold?
The third shell can hold 18 electrons but it fills up to 8. The next 2 go into the fourth shell. Then the rest of the third shell fills.
Hydrogen electron configuration
1
Helium electron configuration
Period 1 Group VIII
2
Lithium electron configuration
2+1
Beryllium electron configuration
2+2
Boron electron configuration
2+3
Carbon electron configuration
2+4
Nitrogen electron configuration
2+5
Oxygen electron configuration
2+6
Fluorine electron configuration
2+7
Neon electron configuration
2+8
Sodium electron configuration
2+8+1
Magnesium electron configuration
2+8+2
Aluminium electron configuration
2+8+3
Silicon electron configuration
2+8+4
Phosphorus electron configuration
2+8+5
Sulfur electron configuration
2+8+6
Chlorine electron configuration
2+8+7
Argon electron configuration
2+8+8
Potassium electron configuration
2+8+8+1
Calcium electron configuration
2+8+8+2
What does the period number tell you?
The period number tells you how many shells there are.
What are valency electrons?
Outer shell electrons
What does the group number tell you?
The group number is the same as the number of valency electrons.
Group VIII
Group VIII elements are unreactive as they all have 8 or 2 outer shell electrons.
Reactions of isotopes
All isotopes of an element have the same number of valency electrons, so their chemical reactions are the same.
Terms for how the electrons are arranged in shells.
Electron arrangement
Electronic configuration
Electron distribution
Electronic structure
