All gases are grouped together. Gases easily form compounds with other elements. Elements within a group have similar properties. Elements within a period have the same number of electrons.
I gave my students this multiple choice question: Which statement best describes the organization of the Periodic Table of the Elements?

Only one answer is correct among these 4 choices:
- All gases are grouped together.
- Gases easily form compounds with other elements.
- Elements within a group have similar properties.
- Elements within a period have the same number of electrons.

Could you tell me which one is correct?

Elements within a group have similar properties.