Atomic Models POGIL Activity.doc.pdf - Karlie Phillips...

Name:__________________________________________________________Date:__________Period:_____
POGIL: Atomic Models and the Development of the Atom
Background:
Models are used in science as a way to represent what we cannot see. They help us work with,
visualize, and understand scientific concepts. However, models are constantly changing as we
develop new technology and continue to make advancements. We are going to study the atom in
this unit, and it is important to learn about the process of developing our most current model.
Model 1: Dalton
Dalton came up with the theory that described atoms in five postulates, meaning, a set of
concepts or theories proposed by scientists. Dalton used experimentation to develop his
postulates through testing gases. He first differentiated atoms via atomic weight. His data
was flawed, however, but he is known as the father of atomic theory due to his immense strides
in this topic. His five postulates are listed below:
1. All elements are composed of tiny indivisible particles called atoms that cannot
be broken down further. *
2. Atoms of a given element are all similar in their physical and chemical
properties. *
3. Atoms of different elements differ in their physical and chemical properties.
4. Atoms of different elements combine in simple, whole number ratios to form
compounds.
5. In chemical reactions, atoms are combined, separated, or rearranged, but never
created, destroyed, or changed.
*Indicates that the postulate is still held as true today.
Dalton’s model summarizes these principles by showing that an
atom is made up of solid, indivisible particles. This was
originally stated by Greek philosopher Democritus, and he
called the indivisible particle atomos (which means indivisible).
However, Democritus did not have any support for his claim.