history of atom guided notes - parkway schools / … o… · · 2012-01-09note on history of the...
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Name_________________________ Date_____________
Note on History of the Atom
� Why is learning about the atom important….? • The atom was considered to be an “imaginary” thing, something that people laughed at!
• Roosevelt trusted Einstein, and funded his secret research known as the “Manhattan Project”
• In a few short years, the idea of an invisible atom had been developed into a city-destroying weapon - the atomic bomb! They figured out they could split atoms apart, and this would release tons of energy!
� The History of the Atom……. o Democritus was the first to suggest that all matter was made of ______________! o The name atom comes from his Greek word,
“______________”, which means not dividable or whole! o Democritus’ ideas were crushed by another Greek Philosopher, named……….
………………______________________!!!!
� Aristotle didn’t believe in atoms o Aristotle asked Democritus questions:
� If we are made of atoms, what holds us together?
� Why can’t we see these atoms?
� Why don’t we fall down like a bag of marbles?
� What’s in between atoms?
� Democritus was unable to answer these questions……. o And so, people continued to think that matter was continuous - your body, the world around us
was one continuous piece…. o This philosophy continued for centuries…….
� Many years later…. o Middle Ages: 5th -16th Century o Alchemy: medieval “chemistry” o All matter made of 4 elements –
_____________ , _____________ , _____________, ____________
� During the 1700’s and 1800’s…. • Scientists were doing large, observable, basic experiments
• They were doing experiments with stoves, pots, ovens, and basic glassware!
• With observable properties came explanations!
• _____________________-the act of reasoning from factual knowledge or evidence
� John Dalton…… (1766-1844)
o A __________________________! o Described what was seen by scientists in terms of _____________________!
� John Dalton theorized that these substances were made of atoms!
o THE ATOMIC THEORY OF MATTER! (1803)
� All _____________________ are made of tiny, solid, indestructible particles known as atoms
� All atoms of one element are the _______________
� Atoms of _________________ elements are different
� Atoms of different elements form compounds in whole number ratios
� Atoms are not created or destroyed in chemical reactions, only how they are combined to form compounds
• John Dalton’s theory was wrong in one respect……..
�John Dalton’s theory was wrong in one respect……..
Atoms are not solid and indestructible like marbles….. � They contain different parts……. � However, scientists did not know this until parts of the atom were discovered…..
What part of the atom do you think was discovered first…..?
�THE _____________________…! Why do you think it was the first part of the atom to be discovered…..?
________________________________________________________________
�Benjamin Franklin in the Early 1800’s! o Lots of basic work with _________________ o Matter has charge! o There are two types of “_____________” in the world:
� + charged objects � charged objects
� Ben Franklin is the first to come up with these names positive & negative. o Franklin didn’t know that these charges were part of the ________________.
�J.J. THOMSON � In 1897, Thomson used a ___________________________________________ (CRT)
to prove that an atom had a ________________________ particle known as an electron’
� He believed that __________________ were distributed throughout an atom
� This model is known as the “__________________________________________”.
Electrons are stuck throughout an atom just like plums are stuck throughout pudding.
Plum Pudding is an English dessert
� Cathode Ray Tube, or Crooke’s Tube
� This was one of the very first experiments to be done with electricity! � __________________ designed this tube in 1879. � The cathode ray (travels from cathode to anode) inside glows � Crookes was convinced this beam consisted of charged particles
� So what are Cathode Rays….?
♣ ________________________, in 1897, answered this question!
♣ Thomson used a Crooke’s tube and two charged plates above and below the beam
♣ Which way do you think the beam bent….?
♣ The Beam was attracted to _____________plate,
and was deflected from _______________ plate!
♣ The beam could also be deflected with a magnet
♣ From this, he said that the beam was made
of ___________________ charged particles,
called ______________________!
♣ He was looking at electrons, which are part of the atom!
�The cathode ray tube was the beginning to the modern day…..
____________________
�Who puts all of this information together into “The Big Picture”?
• J.J. Thomson theorized that these negative and positive particles were part of the
atom!
• We are all made of charge!
• He develops the first working model of the atom,
known as the ______________________________________!
• This rejected ____________________ idea that atoms were solid particles like
marbles that weren’t made of smaller pieces
�Thomson Analogy - ___________________________ Draw:
�Why is Thomson’s model wrong….?
♣ A scientist named Ernest Rutherford figured it out!
♣ He shoots big heavy alpha (_) particles (with + charge) at ultrathin gold foil
♣ He expected most to go through the atom.
♣ Very few were deflected, and some even bounced straight back!
♣ Rutherford described this as a bowling ball being sent at a piece of paper, full
speed, and bouncing back!
�ERNEST RUTHERFORD � In 1908, he performed his famous _____________________________________.
� His experiment proved that an atom is mostly ________________________.
� It also proved that an atom has a small and dense positively charged center called
a _________________________.
�The Gold Foil Experiment….
� Rutherford’s “nuclear” model! Draw:
� What is going on….? � Most of the ______________ particles are going straight through!
� A few of the _____________________________ are bouncing off of something!
� Alpha particles are _______________and _________________________!
o What could they be bouncing off of ?
o They must be bouncing off of something that is….
_____________________________________
Rutherford theorized that all of the protons weren’t scattered about, like in a chocolate
chip cookie, but were all ___________________________ into a tiny, dense __________________,
which he called the ________________________!
�Rutherford Analogy - __________________ Draw:
�What is the relative size of the atom….? ♣ An atomic model the size of Busch Stadium and parking would contain a pea sized nucleus containing
95.95% of the atoms mass.
♣ The _____________ at the pitcher’s mound would be the ____________________, and an
_______________ crawling on the parking lot outside would be an ________________________!
♣ The atom is mostly…..
♣ _______________________________________! _______________________________!
� Structure of the Atom o Inside Nucleus:
� Protons (p+) - have ____________, _______________ charge, & determine identity of ___________________
� Neutrons (n) - have _________________, ___________ charge o Outside Nucleus:
� Electrons (e-) - ________________ charge, ________ mass
� Number of particles in neutral atom • # p+ usually = # e-
• Atomic Number = # p+
• Mass Number = # p+ + # n
� So is this the final model of the atom today… __________! o A scientist named ________________________, a great friend of Einstein, noticed
something weird about _____________________.
o A hydrogen atom consists of ____________________ orbiting ______________….
o Atoms can give off light when they are excited with _________________!
o Think about light bulbs, neon lights, headlights….
With one electron, how many different types of energy or colors of light do you think
hydrogen can give off….?
� NEILS BOHR � He wondered about the exact location of _______________in an atom.
� He concluded in 1913 that an electron had a certain amount of energy
which keeps an electron moving around the nucleus in a region called an
__________________ level.
� He described an atom much like the ___________________________ in
that electrons orbit around the nucleus in energy levels just as
_________________orbit around the sun
� Bohr Analogy - ______________________ Draw:
� Bohr came up with a new model for the atom…
� Bohr suggested that _____________ could move to many locations or “_____________levels”
within the atom!
� The electron was _______________ to more than one location in the atom!
� In Bohr’s Model of the atom, electrons orbit the nucleus like planets orbit the sun. It is called
THE ____________________________MODEL.
� When electrons jump up to different energy levels, they eventually fall back down and give off
_______________________!
� Electrons in Energy Levels Level maximum number
of electrons
1 ____
2 ____
3 ____
4 ____
� WAVE MODEL or ELECTRON CLOUD-Modern Atomic Theory � In 1926, it was stated that it is impossible to know the exact
location and motion of an electron or small particle= Heisenburg Uncertainty Principle.
� Electrons don’t orbit the nucleus in simple, well-defined paths. This is why chemists often show electron orbitals as
cloudy regions. The more dots in the cloud, the more likely an electron would be found there.
� Electron Cloud Analogy - _____________________________
� Electron Cloud Model
• Electrons not in fixed orbits (like Bohr’s model), instead is areas or
“clouds”
• Shows where we are most likely to find an electron
• Most current model
Draw the 4 different Models: