ACT Preparation / Unit 22 ACT 2109 short lesson, about 20 seconds
Atoms, Elements and Compounds
Captions available
The idea
An atom is the smallest unit of an element. Its nucleus holds protons and neutrons, with electrons around it, and the number of protons, the atomic number, identifies the element.
In practice
Any atom with eight protons is oxygen; water is a compound of hydrogen and oxygen.
Where people slip
An element cannot be broken down by chemical change; a compound can, into its elements.
Your place on the trail
Every lesson rests on earlier ones and opens later ones. Tap any to jump.
Builds on
- Nothing. This is a starting point.
Something wrong in this lesson? Flag it · Sources for ACT Preparation