Science is based off of observations A Scientific Law is a summary of what is seen in observations A Scientific Theory is an explanation of why these observations are occurring Both laws and theories are tested by using them to predict what would happen in certain situations ID: 689500
Download Presentation The PPT/PDF document "Atomic Theory Chapter 4 Atomic Theory" is the property of its rightful owner. Permission is granted to download and print the materials on this web site for personal, non-commercial use only, and to display it on your personal computer provided you do not modify the materials and that you retain all copyright notices contained in the materials. By downloading content from our website, you accept the terms of this agreement.
Slide1
Atomic Theory
Chapter
2Slide2
Atomic Theory
Science is based off of observations.
A Scientific Law is a summary of what is seen in observations.
A Scientific Theory is an explanation of why these observations are occurring.
Both laws and theories are tested by using them to predict what would happen in certain situations.Slide3
Atomic Theory
-Explains why all matter acts as it does because it is composed of tiny particles called atoms, the basic building blocks of all matter
First theorized by Democritus ~400 BC in ancient Greece.
He thought that matter could NOT be divided infinitely. You had to reach a smallest possible piece. He named this piece an atom, which meant indivisible or can’t be cut.Slide4
More Democritus
He and his followers, atomists, said atoms were small hard particles all made of the same material, but different sizes and shapes.
They were also always moving and capable of joining together.
Since this was ancient Greece, He and the atomists had no way of ever proving his theories and few people believed it.Slide5
Elements and Compounds
Lots of research through alchemy went into different substances.
Pure substances that could be broken down into smaller substances were called
compounds
.
Pure substances that couldn’t be broken down were called
elements
.Slide6
Law of Conservation of Mass
A chemical reaction does not change the mass of the matter present.
The mass of the reactants is equal to the mass of the products.
This is true even if a different phase of matter is created
.
This is also called
Lavoisier’s
law
Developed in the lat
e 1780’sSlide7
Law of definite proportions
1790’s
All
pure compounds have exactly the same proportions by mass of elements regardless of size
Water is always 2 hydrogen atoms to every 1 oxygen atom
By mass that is 2 (g) H : 16 (g) O Slide8
Dalton’s Model (1803)
people started to accept the idea of atoms because of his experiments
He worked with gases and found that they acted as though they were made of solid microscopic particles
all elements are made of atoms (indivisible and indestructible)
atoms of the same element are exactly alike
atoms of different elements are different
compounds are formed by joining two or more
elementsSlide9
Law of multiple proportions
Also
known as Dalton’s
Law
The same elements may combine differently to form different compounds.
Hydrogen and oxygen may make water, but they also may make hydrogen peroxide.
Atoms may join together in different manors.Slide10
John DaltonSlide11
Thomson’s Cathode RaySlide12
Thomson’s Model (1897)
found negative particles could come from neutral elements
atom is made of smaller things (+ & -), and is divisible
successfully separated negative particles (electrons) but could not separate the positive particle (protons)
“plum pudding model” negative particles floating in a positively charged gel like materialSlide13
Plum Pudding Model- Thomson
Positive Gel
Negative
ParticlesSlide14
Sir J. J. Thomson
The sir means
he was knightedSlide15
Rutherford’s Model (1911)
fired protons at a sheet of gold foil most went through unaffected, some bounced away
there is a small dense area of positive particles at the center of the atom- the nucleus
electrons are scattered near the outside of the atom with mostly empty space between the nucleus and the electronsSlide16
Gold Foil Experiment
Radioactive source
Gold foilSlide17
Rutherford’s Model
nucleus
(small dense
positive area)
electrons
Empty SpaceSlide18
Ernest RutherfordSlide19
Bohr Model (1913)
electrons move in definite orbits around the nucleus
these orbits or energy levels are located at certain distances from the nucleus Slide20
Bohr’s Model
nucleus
ElectronsSlide21
Neils BohrSlide22
Wave Model (present day)
based on complex math equations
orbits are more complex than originally thought
de Broglie
stated that electrons (particles) have
wave properties
, and he viewed these as standing waves, like those produce when a guitar string is plucked (classical physics.)
Schrodinger
assumed that the electron in Hydrogen behaves as a standing wave.
Slide23
Wave Model (continued)
When Schrodinger’s equation is analyzed, many solutions are found.
Each solution represents an atomic orbital.
An
atomic orbital
is the most
probable
location for finding an electron.Slide24
What is an orbital?
It is not a Bohr orbit (not moving in a circular path.)
How is the electron moving?
We don’t know!
There is a fundamental limitation to just how precisely we can know both the position and momentum of a particle at a given time
Slide25
This is kind of how we assume an electron travels
e
-Slide26
Heisenberg Uncertainty Principle
The more accurately we know the particle’s position, the less accurately we can know it momentum and vice versa.
We can’t know the exact motion of the electron around the nucleus.
The area that an electron orbits is called an “electron cloud”Slide27
Louis de Broglie Erwin SchrodingerSlide28
Werner Heisenberg