AQA · GCSE · Chemistry
Course version: 8462 · Version from Sept 2018
For example, the electronic structure of sodium is 2,8,1 or showing two…
Full specification wording
Electronic structure: For example, the electronic structure of sodium is 2,8,1 or showing two electrons in the lowest energy level, eight in the second energy level and one in the third energy level.
Sodium has atomic number 11, so a neutral sodium atom contains 11 electrons.
Checked against the AQA 8462 specification (opens in a new tab) on .
- Point 3 of 3
- 2 key terms
Study notes
From the checked teaching notes for this specification point.
The idea
Sodium has atomic number 11, so a neutral sodium atom contains 11 electrons. These electrons fill the lowest available energy levels first. The first energy level holds a maximum of two electrons, so it is filled with two. The second energy level holds up to eight electrons in this context, so it is filled with eight. The remaining one electron occupies the third energy level. The electronic structure is therefore written as 2,8,1, meaning two electrons in the lowest energy level, eight in the second energy level and one in the third energy level. A diagram would show a nucleus with two electrons on the first shell, eight on the second and one on the third. The single outer electron explains why sodium is in Group 1 and forms a 1⁺ ion.
What earns the marks
- Sodium has 11 electrons because its atomic number is 11.
- The first energy level contains two electrons and is filled first.
- The second energy level contains eight electrons.
- The third energy level contains the remaining one electron.
- The electronic structure of sodium is written as 2,8,1 or shown as 2, 8 and 1 electrons in successive shells.
Common mistakes and how to put them right
Writing sodium as 8,2,1.
Put it right by filling the innermost level first, giving 2,8,1.
Placing more than two electrons in the first energy level.
Put it right by limiting the first level to two electrons.
Forgetting that sodium has 11 electrons.
Put it right by using the atomic number to determine the total number of electrons.
Exam tips
- Use the atomic number to work out the total number of electrons before arranging them.
- For main-group elements, the number of electrons in the outer shell equals the group number.
- When drawing sodium, show one electron alone in the third shell to make the Group 1 behaviour clear.
Try the lesson
The start of the Electronic structure: For example, the electronic structure of sodium is 2,8,1 or 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
Sodium has the electronic structure 2,8,1. How many electrons are in the second energy level of a sodium atom?
Listen
Sodium has atomic number 11, so a neutral sodium atom contains 11 electrons. These electrons fill the lowest available energy levels first. The first energy level holds a maximum of two electrons, so it is filled with two. The second energy level holds up to eight electrons in this context, so it is filled with eight. The remaining one electron occupies the third energy level. The electronic structure is therefore written as 2,8,1, meaning two electrons in the lowest energy level, eight in the second energy level and one in the third energy level. A diagram would show a nucleus with two electrons on the first shell, eight on the second and one on the third. The single outer electron explains why sodium is in Group 1 and forms a 1⁺ ion. A strong answer earns marks for these points. Sodium has 11 electrons because its atomic number is 11. The first energy level contains two electrons and is filled first. The second energy level contains eight electrons. The third energy level contains the remaining one electron. A common slip: Writing sodium as 8,2,1. Instead, filling the innermost level first, giving 2,8,1. Exam tip: Use the atomic number to work out the total number of electrons before arranging them.
See it
Put it in order
Put these steps in the order they happen.
- 1. One outer electron: Group 1, forms a 1⁺ ion
- 2. Electronic structure written as 2,8,1
- 3. First energy level filled first: 2 electrons
- 4. Third energy level: remaining 1 electron
- 5. Sodium: atomic number 11
- 6. 11 electrons in a neutral atom
- 7. Second energy level: 8 electrons
Key words
Say what each word means before you turn the card.
Electronic structure of sodium
Try answering aloud or in your head before turning the card.
Filling of energy levels
Try answering aloud or in your head before turning the card.
See every definition
- Electronic structure of sodium
- Written as 2,8,1, meaning two electrons in the lowest energy level, eight in the second energy level and one in the third energy level.
- Filling of energy levels
- Electrons fill the lowest available energy levels first, with the first energy level holding a maximum of two electrons.
Label the diagram
Some boxes have lost their names. Pick the right name for each number.
1Box 1
2Box 2
3Box 3
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