Video narration
How can invisible atoms explain the solid things around you? Imagine separate building blocks. Dalton's atomic theory treated each as a tiny atom: one kind made an element, joined groups made compounds. Not literal toy pieces. He said each element had its own alike atoms, different elements had different atoms, compounds joined them in whole-number ratios, and reactions rearranged atoms. In ordinary reactions, atoms join in fixed ratios to form compounds; rearrange them, and new substances appear without creating or destroying atoms. That neat, indivisible picture explains ordinary chemical reactions. But here is the turn: atoms have smaller parts, and atoms of one element can have different masses-these are isotopes. Nuclear reactions, however, can change one element into another. So how did Dalton explain matter? As atoms, like building blocks, combining in whole-number patterns and rearranging in reactions-a powerful first model, not the final one.