1. History of Atom
Science classroom Extra video on history of atom

2. The History of Atomic Theory
The atom the smallest particle of an element that has the same the properties of the element
Early ideas about matter
Greek philosophers believed that matter was made of atomos that were the smallest pieces of matter.
Aristotle believed matter was made of
different combinations of earth, air,
fire, and water.
Alchemists experimented with matter and
tried to turn common metals into gold.
Their activities marked the beginning of
our understanding of matter.

3. Ancient Greeks
Greek philosopher Democritus believed everything was made up of tiny particles in empty space.
He called them Atomos, meaning “Uncuttable”.
He did not use experiments to support his ideas, just reason and logic.
Philosopher Aristotle disagreed because he didn’t believe empty space could exist.
Denial of existence of atoms persisted for 2000yr

4. Dalton’s Atomic Theory
All matter is made of small particles called atoms.
Atoms cannot be created, destroyed, or divided into smaller particles.
All atoms of the same element are identical in mass and size, but they are different in mass and size from the atoms of other elements.
Compounds are created when atoms of different elements link together in definite proportions.
John Dalton school teacher ( ) developed a theory that was a new way of explaining matter. Conducted experiements
He studied gases that make up Earth’s atmosphere.
Based on his studies, he suggested that:
matter is made of small, hard spheres
that are different for different elements
the smallest particle of an element is called an atom

5. Early Ideas about Matter and Atoms
Researcher
Idea
Model
Ancient Greeks
Atomos- smallest piece of matter
(n/a)
John Dalton
( )
particles are small hard spheres that are different for different elements
J. J. Thomson
( )
Atoms have smaller particles called electrons (= raisin bread model)
Ernest Rutherford ( )
 electrons move around the nucleus and the nucleus is made up of protons and neutrons
Neils Bohr ( )
Electrons circle the nucleus in predetermined shells
Ancient Greeks: Democritus believed everything was made up of tiny particles in empty space. Atomos. Uncuttable. No proof, just theory
Aristotle disagreed. Didn’t believe empty space could exist. Denial for 2000yr
John Dalton school teacher ( ) developed a theory that was a new way of explaining matter. Conducted experiements
He studied gases that make up Earth’s atmosphere.
Based on his studies, he suggested that:
matter is made of small, hard spheres
that are different for different elements
the smallest particle of an element is called an atom

6. J. J. Thomson ( )
studied electric currents in gas discharge tubes (like today’s fluorescent lights). From his studies, he determined that the currents were streams of negatively charged particles (later called electrons).
hypothesized that atoms were made
of smaller particles.
proposed “raisin bun” model.
(positively charged bun with negatively
charge particles spread out in it like
raisins.)
JJ Thompson, British physicist who studied electrical current in cthode ray tubes
Cathode rays were streams of negatively charged particles
All substances produced these particles

7. Ernest Rutherford ( )
Shot positively charged particles through thin sheet of gold. Some went straight through, but some bounced back
He suggested that the deflection of the charged particles was because the atom contained a tiny dense nucleus.
and electrons moved
around the nucleus.
Scientist from New Zealand
Exposed thin sheet of gold to a stream of high speed particles with a positive charge, (alpha particles). The alpha particles cted like tiny bullets. Some particles went through and hit screen on other side., consistent with Thomson’s model (bullet through a muffin) but some rebounded from the foil like a ball bouncing off a wall. Discovered nucleus – tiny dense positively charged center of atom.
According to him, all mass was in nuc

8. Niels Bohr ( )
He studied gaseous samples of atoms, which were made to glow by passing an electric current through them.
Based on his observations, Bohr proposed
that electrons surround
the nucleus in specific
“energy levels” or “shells.”
Danish physicist, student in Rutherford’s lab,
Each gas produced a characteristic spectrum of light as a result, called a line spectrum. Light emitted by the gases was a result of high-energy electrons releasing energy. But electrons of a given gas emitted light only of certain wavelengths.  energy levels

9. Make some notes
Using graphic organizer

10. Atom Sorting Activity
Atom Sorting Activity

11. The Atom
What is an atom? Ted Ed: How small is an atom?
Ted Ed invisible video
How small is an atom
What is an atom? Monkey see

12. Parts of the Atom
All atoms are made up of three smaller particles called subatomic particles:
electrons
neutrons
protons  

13. Some have a charge protons (+) are attracted to electrons (-)
Atoms are neutral: number of electrons equals the number of protons.
e.g. 5 + and 5 – makes 0 charge

14. Subatomic Particles have mass
protons and neutrons have much more mass than electrons (about 1800 times more!) 

15. Atoms have a Nucleus
Protons and neutrons are found together in the centre of the atom called the nucleus.
The nucleus is a very small part of an atom and has a positive charge because of the protons.

16. Electrons
Electrons circle the nucleus in special pathways called energy levels or shells.
This region is big (it takes up 99.99% of the atom).
An electron is like a spread-out negative charge that exists in the whole region at once- it is not a fast-moving particle racing around the nucleus.
An electron is like a spread-out negative charge that exists in the whole region at once- it is not a fast-moving particle racing around the nucleus.

17. Electrons and Quantum Physics… Everywhere and Nowhere at the Same Time

18. Check your Understanding
What are the three subatomic particles?
Compare and contrast the electron and proton

19. Atomic Number = Number of Protons

20. Atomic Mass = Protons + Neutrons

21. Build your own atom

22. Atomic Theory Continues to Develop
According to Dalton’s theory, atoms were indivisible and indestructible. Then Thomson discovered the electron and Rutherford discovered the nucleus, which was later found to be made up of neutrons and protons. The atom was not indivisible at all: it was made up of even smaller particles –subatomic particles. Discoveries that some of these subatomic particles were made up of still smaller particles.

23. Protons and Neutrons are composite particles and are made up of Quarks and Gluons

24. Quarks
Quarks are elementary particles, meaning they cannot be split apart into smaller particles
6 difference types (flavours) of quarks classified by their properties: mass, electric charge, etc
Atomic Theory Continues to Develop:
According to Dalton’s theory, atoms were indivisible and indestructible. Then Thomson discovered the electron and Rutherford discovered the nucleus, which was later found to be made up of neutrons and protons. The atom was not indivisible at all: it was made up of even smaller particles –subatomic particles. Discoveries that some of these subatomic particles were made up of still smaller particles.
There are six quarks, but physicists usually talk about them in terms of three pairs: up/down, charm/strange, and top/bottom. (Also, for each of these quarks, there is a corresponding antiquark.)
Quarks have the unusual characteristic of having a fractional electric charge, unlike the proton and electron, which have integer charges of +1 and -1 respectively. Quarks also carry another type of charge called color charge, which we will discuss later.
The most elusive quark, the top quark, was discovered in 1995 after its existence had been theorized for 20 years.

25. Gluons
protons and neutrons also contain elementary particles called gluons
they "glue" quarks together, forming protons and neutrons

26. Leptons
Leptons are elementary particles that appear to be point-like particles without internal structure.
Electrons are a type of Lepton
six types of leptons: 3 have electrical charge (electron-like) and 3 do not (neutrinos).
Unlike protons and neutrons, electrons are themselves elementary particles.
Nuclei are made up of protons and neutrons. In turn, protons and neutrons are made up of point-like particles called the "up" and "down" quarks. As far as we know electrons are elementary particles; that is, they appear to be point-like particles without internal structure
The key difference between quarks and leptons is that quarks experience the strong force while leptons do not

27. Leptons
The other two charged leptons are the muon( ) and the tau( ), which are charged like electrons but have a lot more mass.
The other leptons are the three types of neutrinos ( ). They have no electrical charge, very little mass, and they are very hard to find.
Quarks are sociable and only exist in composite particles with other quarks, whereas leptons are solitary particles.
Think of the charged leptons as independent cats with associated neutrino fleas, which are very hard to see.

28. Research Continues
TRIUMF cyclotron at UBC was built to research the particles that make up matter.
Electromagnets in the cyclotron accelerate protons to extraordinary speeds.
Resulting proton beam is allowed to collide with various material, and specialized detectors provide data about the products of the collisions.
world's largest cyclotron particle accelerator