AQA · A-Level · Chemistry
Course version: 7405 · Version from Sept 2016
An element is classified as s, p, d or f block according to its position…
Full specification wording
Classification: An element is classified as s, p, d or f block according to its position in the Periodic Table, which is determined by its proton number.
The Periodic Table is built in order of increasing proton number, and each element's position follows from its electron configuration.
Checked against the AQA 7405 specification (opens in a new tab) on .
- 3 key terms
Study notes
From the checked teaching notes for this specification point.
The idea
The Periodic Table is built in order of increasing proton number, and each element's position follows from its electron configuration. The block is named after the sub-shell that receives the highest-energy electron: Groups 1 and 2 are filling an s sub-shell and form the s block; Groups 3 to 0 are filling a p sub-shell; the transition series are filling a d sub-shell; the lanthanides and actinides are filling an f sub-shell. The period number is the highest principal energy level occupied. In the s and p blocks, the group number (1 to 7) equals the number of outer-shell electrons, whereas Group 0 elements have a full outer shell. Helium is an exception: it is placed above the noble gases due to its inert chemical behaviour, but its 1s² configuration makes it an s-block element.
What earns the marks
- Stating that the elements are arranged in order of increasing proton number.
- Identifying the block from the sub-shell holding the highest-energy electron.
- Deducing the period from the highest occupied principal energy level.
- Placing an element correctly from a given electron configuration.
Common mistakes and how to put them right
Ordering the table by relative atomic mass rather than by proton number.
Placing helium in the p block because it sits above the noble gases, when 1s² makes it s block.
Assuming Group 0 elements have zero outer electrons rather than a full outer shell.
Exam tips
- Write the full configuration before answering; the block, period and group all read straight off it.
- Remember the two d-block exceptions, chromium and copper, which are examined regularly.
Try the lesson
The start of the Classification: An element is classified as s, p, d or f block according to its position in the Periodic Table, which is determined by its proton number. lesson, made from checked teaching notes for this specification point.
Have a go first
Potassium has proton number 19. Which block of the Periodic Table does potassium belong to?
Listen
The Periodic Table is built in order of increasing proton number, and each element's position follows from its electron configuration. The block is named after the sub-shell that receives the highest-energy electron: Groups 1 and 2 are filling an s sub-shell and form the s block; Groups 3 to 0 are filling a p sub-shell; the transition series are filling a d sub-shell; the lanthanides and actinides are filling an f sub-shell. The period number is the highest principal energy level occupied. In the s and p blocks, the group number (1 to 7) equals the number of outer-shell electrons, whereas Group 0 elements have a full outer shell. Helium is an exception: it is placed above the noble gases due to its inert chemical behaviour, but its 1s² configuration makes it an s-block element. A strong answer earns marks for these points. stating that the elements are arranged in order of increasing proton number. identifying the block from the sub-shell holding the highest-energy electron. deducing the period from the highest occupied principal energy level. placing an element correctly from a given electron configuration. Exam tip: Write the full configuration before answering; the block, period and group all read straight off it.
See it
Key words
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s, p, d and f blocks
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proton number ordering
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helium as an exception
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See every definition
- s, p, d and f blocks
- An element is classified into one of these according to its position in the Periodic Table, which is determined by its proton number.
- proton number ordering
- The Periodic Table is built in order of increasing proton number, and each element's position follows from its electron configuration.
- helium as an exception
- It is placed above the noble gases due to its inert chemical behaviour, but its 1s² configuration makes it an s-block element.
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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