Organising the Periodic Table
Elements are arranged by atomic number in periods and groups.
About this topic
The periodic table arranges elements in order of increasing atomic number in horizontal rows called periods and vertical columns called groups. Elements in a group have similar properties because they have the same number of valence electrons; period number equals the number of electron shells.
The table is divided into blocks (s, p, d and f) that match the subshell being filled. Group numbers 1 and 2 are the s-block, 13 to 18 the p-block, the centre is the d-block, and the two rows below are the f-block. Moving across a period, properties change gradually from metal to non-metal, then repeat in the next period, hence the word periodic. Mendeleev predicted undiscovered elements from gaps in his table.
For example, lithium, sodium and potassium are in group 1 and all are soft, reactive metals that form +1 ions. If you know that element X is in period 3 and group 16, you can say it has three shells and six valence electrons, so it is sulfur.
The table is a map that lets you predict reactivity, bonding and formulas without memorising every element. A common misconception is that the order is by atomic mass; it is by atomic number, which resolves the tellurium and iodine mismatch. Also hydrogen sits in group 1 but is a non-metal.
Key ideas
- Rows are periods
- Columns are groups with similar properties
- Mendeleev predicted missing elements
Quick check
Use cases: where Organising the Periodic Table helps
- Homework: review the key idea behind Organising the Periodic Table before you start a problem set.
- Exam revision: use the quick check to test whether you can recall Organising the Periodic Table without notes.
- Visual learning: play with the interactive lab to see how Organising the Periodic Table changes when you adjust its inputs.
- Teaching a friend: explain Organising the Periodic Table in your own words, then compare your version with the key ideas.
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Frequently asked questions
What is Organising the Periodic Table?
Elements are arranged by atomic number in periods and groups.
What will I learn in Organising the Periodic Table?
Rows are periods. Columns are groups with similar properties. Mendeleev predicted missing elements.
Is Organising the Periodic Table part of Chemistry?
Yes. It is one of 150 Chemistry topics on LearnViz HighSchoolEdu, with 3 key ideas, a live animation and a quick check.
Does the Organising the Periodic Table lab work on a phone or tablet?
Yes. The animation resizes to fit your screen and supports touch, so you can drag, tap and slide with your finger.
How should I study Organising the Periodic Table?
Read the summary and key ideas first, play with the interactive lab to see the idea in motion, then answer the quick check. If you get a question wrong, go back to the key idea it tests.
Do I need an account, and is my progress saved?
No account is needed. Marking a topic as learned is saved in your own browser, so it stays on that device and is not sent to a server.