Density as mass per volume
Two objects can have the same size but very different masses because their densities differ.
Read the picture
The illustration is conceptual. It shows relationships, not a literal photograph of atoms, orbitals or microscopic particles.
MendeleevUse the picture to make a prediction first. Then open the deeper science page and see where the simple model works—and where it stops working.
Core Science →
How to use this page
Start by identifying the quantity, element or phenomenon being studied, then connect it with a concrete situation. A scientific formula becomes much easier to understand once every term and unit has a clear physical meaning.
Mendeleev’s habit: always check the order of magnitude. A calculation can look correct while giving a physically impossible result when a unit has been forgotten or converted incorrectly.