AQA · GCSE · Combined Science
Course version: 8464 · Version from Sept 2018
Showing two electrons in the lowest energy level, eight in the second…
Full specification wording
Electronic structure: showing two electrons in the lowest energy level, eight in the second energy level and one in the third energy level.
Electrons occupy energy levels (shells) around the nucleus, filling the lowest available level first.
Checked against the AQA 8464 specification (opens in a new tab) on .
- Point 2 of 2
- 3 key terms
Study notes
From the checked teaching notes for this specification point.
The idea
Electrons occupy energy levels (shells) around the nucleus, filling the lowest available level first. For the first 20 elements, the pattern is up to 2 electrons in the first level, 8 in the second, 8 in the third, and up to 2 in the fourth. Sodium (atomic number 11) therefore has 2, 8, 1. You show this as a dot-and-cross diagram with a small circle for the nucleus, labelled with the symbol, and arcs for each level carrying the correct number of electrons. The third level is the outer shell for sodium, so it has one outer electron, which explains its position in Group 1 and its tendency to form a 1⁺ ion.
What earns the marks
- State that electrons are arranged in energy levels (shells) around the nucleus, with the lowest energy level filled first.
- Give the correct occupancy for sodium as 2 electrons in the first level, 8 in the second and 1 in the third.
- Draw a diagram with a central nucleus labelled with the symbol and separate arcs or circles for each energy level.
- Place the correct number of electrons on each arc, using dots and/or crosses consistently.
- Identify the outer-shell electron and link it to sodium's Group 1 position.
Common mistakes and how to put them right
Assuming the third shell can hold all remaining electrons for the first 20 elements.
Put it right: The third shell holds up to 8 before the fourth shell begins filling.
Putting 9 electrons in the second level for sodium.
Put it right: The second level holds a maximum of 8.
Drawing the nucleus without a label.
Put it right: Label the centre with the symbol Na.
Exam tips
- Count the total electrons on your diagram and check it equals the atomic number (11 for sodium).
- Remember the filling order for the first 20 elements is 2, 8, 8, 2.
Try the lesson
The start of the Electronic structure: showing two electrons in the lowest energy level, eight in the second energy level and one in the third energy level. lesson, made from checked teaching notes for this specification point.
Have a go first
An atom has the electronic structure 2,8,1. How many electrons are in the second energy level of this atom?
Listen
Electrons occupy energy levels (shells) around the nucleus, filling the lowest available level first. For the first 20 elements, the pattern is up to 2 electrons in the first level, 8 in the second, 8 in the third, and up to 2 in the fourth. Sodium (atomic number 11) therefore has 2, 8, 1. You show this as a dot-and-cross diagram with a small circle for the nucleus, labelled with the symbol, and arcs for each level carrying the correct number of electrons. The third level is the outer shell for sodium, so it has one outer electron, which explains its position in Group 1 and its tendency to form a 1⁺ ion. A strong answer earns marks for these points. State that electrons are arranged in energy levels (shells) around the nucleus, with the lowest energy level filled first. Give the correct occupancy for sodium as 2 electrons in the first level, 8 in the second and 1 in the third. Draw a diagram with a central nucleus labelled with the symbol and separate arcs or circles for each energy level. Place the correct number of electrons on each arc, using dots and/or crosses consistently. A common slip: Assuming the third shell can hold all remaining electrons for the first 20 elements. Instead, the third shell holds up to 8 before the fourth shell begins filling. Exam tip: Count the total electrons on your diagram and check it equals the atomic number (11 for sodium).
Key words
Say what each word means before you turn the card.
Electronic structure
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Energy levels and shells
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Periodic table groups
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See every definition
- Electronic structure
- The arrangement of electrons in energy levels around the nucleus, with the lowest energy level filled first.
- Energy levels and shells
- Levels around the nucleus that hold up to 2 electrons in the first, 8 in the second, 8 in the third and up to 2 in the fourth for the first 20 elements.
- Periodic table groups
- An element's position is linked to its number of outer-shell electrons, so sodium with one outer electron is in Group 1.
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