C1 Atomic structure: Electronic structure
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Electronic structure (configuration)
- refers to the way the electrons are arranged on the electron shells (energy levels) around the nucleus.
Note:
The electron shell closest to the nucleus is called the 1st shell or the lowest energy level.
The electron shell furthest away from the nucleus is called the outer shell or highest energy level.
Rules to remember:
- the 1st shell (closest to the nucleus) takes maximum 2 electrons
- the 2nd shell takes maximum 8 electrons
- the 3rd shell takes maximum 8 electrons
How do we work out the electronic structure?
Example:
lithium atom
Reminder:
The number of protons = the number of electrons
So, in the case of lithium, there are 3 electrons which get arranged like this:
3Li → 2, 1 (correct) - this means 2 electrons in the 1st shell, 1 electron in the 2nd shell
The electrons first occupy the electron shell closest to the nucleus.
3Li → 1, 2 (wrong) 3Li → 3 (wrong)
The arrangement of electrons in lithium (Li 2,1) can also be shown with diagrams:
Q1. What is the maximum number of electrons in the first electron shell?
2
Q2. What is another term used for naming the first electron shell?
lowest energy level
Q3. What is the maximum number of electrons in the second electron shell?
8
Q4. What is the maximum number of electrons in the third electron shell?
8
Q5. The figure below shows information about an atom of boron.
Write down the electronic configuration for a boron atom.
B 2, 3
Q6. The figure below shows information about an atom of beryllium.
Write down the electronic configuration for a beryllium atom.
Be 2, 2
Q7. The figure below shows information about an atom of carbon.
Write down the electronic configuration for a carbon atom.
C 2, 4
Q8. The figure below shows information about an atom of nitrogen.
Write down the electronic configuration for a nitrogen atom.
N 2, 5
Q9. The figure below shows information about an atom of boron.
Write down the electronic configuration for a boron atom.
B 2, 3
Q10. The figure below shows information about an atom of carbon.
Write down the electronic configuration for a carbon atom.
C 2, 4
Q11. The figure below shows information about an atom of aluminium.
Write down the electronic configuration for an aluminium atom.
Al 2, 8, 3
Q12. The figure below shows information about an atom of argon.
Write down the electronic configuration for an argon atom.
Ar 2, 8, 8
Q13. The figure below shows information about an atom of sulfur.
Write down the electronic configuration for a sulfur atom.
S 2, 8, 6
Q14. The figure below shows information about an atom.
Write down the electronic configuration for this atom. Use the periodic table to identify the atom.
2, 6 Oxygen
Q15. The figure below shows information about an atom.
Write down the electronic configuration for this atom. Use the periodic table to identify the atom.
2, 8, 5 Phosphorus
Q16. The figure below shows information about an atom.
Write down the electronic configuration for this atom. Use the periodic table to identify the atom.
2, 8, 7 Chlorine
Q17. The figure below shows information about an atom.
Write down the electronic configuration for this atom. Use the periodic table to identify the atom.
2, 8 Neon
Q18. The figure below shows information about an atom.
Write down the electronic configuration for this atom. Use the periodic table to identify the atom.
2, 8, 8, 2 Calcium
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