# Lesson 1

> Matter - Anything that has mass and takes up space

> Elements - simplest pure sub

FINISH LATER

### Dalton’s Atomic Theory

Greeks were very good at observing stuff, but could not prove it

Greeks knew of matter as small particles that cannot be divided, but cannot prove

In 1800s, Englishman named John Dalton saw pattern in numerical data and used that patter as evidence to develop and prove his atomic theory

> Atomic theory - all atoms of the same element are identical and have the same mass, 
atom of one element cannot be changed into another, atoms cannot be created or destroyed chemically, only rearranged.
Every compound has a specific ratio, cannot be different

![Image](https://upload.cafenono.com/image/slashpageHome/20240227/202329_L7TyzRmy9q49mwT9eh?q=75&s=1280x180&t=outside&f=webp)

In 1897, british scientist J.J Thomson discovered atoms contains negatively charged particles

### Electron cloud

In the 1920s, the atomic model was changed again, after scientists determined that electrions do not orbit on a fixed track

### Modern model

1932, James Chadwick

For the site tree, see the [root Markdown](https://slashpage.com/atwnotes.md).