Section 1.3  Page 15
Empedocles' and Democritus' atomic models are not scientific models because they were not based on observations obtained through experimental.  Rather, their models were based on though experiments.
Dalton's atomic model consists of the following five ideas.

• Matter consists of definite particles called atoms.
• Each element is made up of its own type of atom.
• Atoms of different elements have different properties.
• Atoms of  two or more elements can combine in constant ratios to form new substances.
• Atoms cannot be created, destroyed, or subdivided in a chemical change.
a)   Ernest Rutherford

b)   Ernest Rutherford

c)   John Dalton

d)   Ernest Rutherford
a)  The raisins represent the negatively charged electrons in the atom.

b)   The bun represents the atom's positively charged sphere.
a) Democritus' model is the result of a thought experiment.  His model only described the atom as an divisible particle.  Dalton's model is a more detailed description of the atom that includes some of its physical properties.  Dalton's model provided empirical support to Democritus' idea.

b)  the model of the atom was slow to evolve for three reasons.  First, the technology available for probing the atom was limited.  Second, until several hundred years ago, there were few people of independent means who were also interested in science as a hobby, and even fewer who were specifically interests in probing the atom.  third, it took many years for the scientific method to evolve.  The alchemists, who lived during the Middle Ages, were the first group of people to record methodical observations with the purpose of answering a question.
a)   nucleus:  the positively charged centre of the atom

b)   proton: a positively charged subatomic particle found in the nucleus of the atom

c)   electron: a negatively charged subatomic particle found in orbit around the nucleus of the atom

d)   neutron: a subatomic particle with no charge found in the nucleus of the atom
a)  Scientific knowledge is tentative because current models and theories are subject to change as new technology allows us to gather more information.  The atomic model is an excellent example of the tentative nature of science.  The atom has evolved from Democritus' model of an indivisible particle to the current model of a positively charged centre containing protons and neutrons, with electrons in the space surrounding it.  electron behaviour is currently describe using quantum mechanics.

b)  As new technology is developed, scientists can further probe the atom.  Shortly after cathode ray tubes were invented, J.J. Thomson proposed that atoms contain negatively charged particles.  Without the cathode ray tube, electrons may not have been discovered.

c)  Each new generation of scientists' builds on the work of previous generation of scientists.  For example, Chadwick built on Rutherford's model and proposed the presence of neutrons in the nucleus, in addition to protons.