These early scientists were not able to ___ their theories

Democritus proposed that matter is made of small, indivisible objects called ___

He proposed that different types of ___ are made from different types of atoms

John Dalton proposed the ___ theory, which was based on careful observations and ___ of chemical reactions

Dalton's theory states that atoms cannot be divided, ___, or destroyed

It also states that atoms of one ___ are different from atoms of other ___

A(n) ___ is the smallest piece of an element that still represents that element

Atoms were first seen by using a(n) ___ microscope

Thomson discovered that the rays in a(n) ___ were attracted to a(n) ___ charged plate, which means that the rays have a(n) ___ charge

Thomson's atomic model stated that an atom is positively charged ___ with ___ throughout it

Rutherford's students performed an experiment during which they shot ___ particles into a piece of ___ foil

The results showed that most of the particles traveled through the foil, but some bounced to the ___, and a few bounced straight back

Rutherford's resulting atomic model proposed that most of an atom's ___ and ___ charge is concentrated in the center of the atom

The ___ is the small, positively charged area in the center of the atom

In the nucleus is the ___, which is an atomic particle with one positive charge

___ was one of Rutherford's colleagues

Chadwick discovered the ___, a neutral particle that exists in the ___ of an atom

The atomic model of ___ proposed that ___ move in circular orbits, or ___ around the nucleus

When energy is added to an atom, electrons move to higher ___; when energy is released by the electron, it moves back to a lower level

The limitation of Bohr's model is that electrons do not actually move in ___ orbits

In the modern atomic theory, electrons form a(n) ___, which is an area around the ___ in which an electron is likely to be located

An electron cloud is mostly ___ space

Protons and ___ are made of smaller parts called ___

There are ___ types of quarks