Download All matter is made up of tiny particles called atoms

The Atom
Dalton's Atomic Theory
(1803)
1. All matter is composed of extremely small particles called atoms.
2. All atoms of a given element are identical in size, mass, and other
properties. Atoms of different elements differ in size, mass, and other
properties.
3. Atoms cannot be subdivided, created, or destroyed.
4. Atoms of different elements can combine in simple, whole-number ratios
to form compounds.
5. In chemical reactions, atoms are combined, separated, or rearranged.
Adjustments to Dalton's Atomic Theory
We now know that atoms of the same element can have different masses and are called isotopes. Isotopes
have a different number of neutrons than the "average" atom of an element.
We have also discovered the possibility of atomic fission; splitting the atom (Hiroshima & Nagasaki).
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Modern Atomic Theory
1. Elements are composed of atoms, which are extremely small.
2. All atoms of a given element have the same chemical properties and
contain the same number of protons.
3. Compounds are formed by the chemical combination of two or more
different kinds of atoms.
(Whole numbers only)
4. Atoms are the units of chemical change.
http://www.ithaca.edu/faculty/anderson/chem121/modatomc.htm
Def: An atom is the smallest unit of a substance that retains the properties of that substance.
Atoms are composed of three types of particles:
Particles
Symbol
Charge
Location
Protons
Neutrons
Electrons
p+
N0
Positive charge
Neutral (no) charge
Negative charge
Found in the nucleus
Found in the nucleus
Found orbiting the nucleus
e-
Nucleus – The positively charged central region of an atom, composed of protons and neutrons and
containing almost all of the mass of the atom. More simply the nucleus is the “middle part” of an atom
defined by an imaginary boundary separating it from the orbiting electrons.
Rutherford's view of the atom (1914)
http://www.daviddarling.info/encyclopedia/R/Rutherfords_experiment_and_atomic_model.html
http://www.worsleyschool.net/science/files/rutherford/atom.html
Bohr models of various atoms. (1920)
http://www.clickandlearn.org/Gr9_Sci/atoms/modelsoftheatom.html
Quantum model of a sodium atom. (Current)
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Atomic Number- Determined by the number of protons
Atomic Mass Unit- mass of one proton or one neutron (they are about the same)
Atomic Mass- Mass of an atom: determined by adding the protons and neutrons
(Actually this number is an average; re. isotopes)
Atomic Number
Atomic Symbol
Atomic Mass
The number of protons is equal to the number of electrons
p+ = e-
The mass number minus the atomic number equals the number of neutrons
mass # - atomic # = N0
Orbital- three-dimensional region about the nucleus in which a particular electron can be found.
Quantum numbers- numbers that specify the properties of atomic orbitals and of their electrons.
Principal Quantum number- indicates the main energy levels surrounding a nucleus, sometimes
referred to as shells or orbitals. (1,2,3,4,5,6,7) Larger numbers are farther away from the nucleus and
electrons found here have more energy.
Orbital quantum number- indicates the shape of an orbital. Often referred to as sublevels or subshells.
(s,p,d,f in order of increasing energy)
s orbitals can hold 2 electrons
p orbitals can hold 6 electrons
d orbitals can hold 10 electrons
f orbitals can hold 14 electrons
Magnetic quantum number- indicates the orientation of an orbital about the nucleus. (x,y.z coordinates)
Spin quantum number- indicates the spin of an electron (+1/2, or -1/2)
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Pictures of Atomic Orbitals
Atoms are mostly empty space. If the nucleus of an atom had the diameter of a dime, the outer edge of the
atom would be about 50 yards away.
If a proton were enlarged to the size of the head of a pin, the outer edge of the atom would be about 100
meters away.
This is a very distorted model of the atom.
If this picture were drawn to scale:
And if the protons and neutrons were a centimeter in diameter;
Then the electrons would be less than the diameter of a hair; and
The entire atom's diameter would be greater than the length of 30 football fields!
If an atom were as large as a football stadium, the nucleus would be the size of a small ladybug crawling
across the 50-yard line. In spite of this size difference, virtually an of the mass of an atom is concentrated in
its nucleus. One electron, which has a negative charge, weighs only 1/1836 as much as the lightest of all
nuclei, that of the hydrogen atom (proton).
In addition, all the particles (protons, neutrons, and electrons) are constantly in motion.
Rutherford's Gold Foil Experiment
http://www.rsc.org/chemsoc/timeline//pages/1911.html
1911- Ernest Rutherford publishes his atomic theory describing the atom as having a central
positive nucleus surrounded by negative orbiting electrons. This model suggested that most of the
mass of the atom was contained in the small nucleus, and that the rest of the atom was mostly
empty space. Rutherford came to this conclusion following the results of his famous gold foil
experiment. This experiment involved the firing of radioactive particles through minutely thin metal
foils (notably gold) and detecting them using screens coated with zinc sulfide (a scintillator).
Rutherford found that although the vast majority of particles passed straight through the foil
approximately 1 in 8000 were deflected leading him to his theory that most of the atom was made
up of 'empty space'.
What percentage of the volume of an atom is just empty space?
Click for Answer:
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Take an online Element Quiz
If you know of some information you think should be included on this page, please
know!!
Interactive Periodic Charts:
http://www.chemicalelements.com/groups/halogens.html
http://www.webelements.com/
http://www.chemicool.com/
http://www.ktf-split.hr/periodni/en/
go on to learn about the Interaction of Matter
let me
Sources:
http://nwscc.cc.al.us/distance/bio103/topic3/3/sld001.htm A good PowerPoint presentation about atoms
http://www.colorado.edu/physics/2000/waves_particles/wavpart2.html cool particle applet
http://www.howstuffworks.com/framed.htm?
parent=atom.htm&url=http://chipo.chem.uic.edu/web1/ocol/SB/1-2.htm more info on orbitals & shapes
http://www.chemguide.co.uk/atoms/properties/gcse.html#top A SIMPLE VIEW OF ATOMIC
STRUCTURE
http://www.biologylessons.sdsu.edu/classes/lab2/index.html
http://press.web.cern.ch/pdg/cpep/big_question.html how do atoms/molecules "stick" together
http://neon.chem.ox.ac.uk/vrchemistry/AMM/HTML/page01.htm an excellent tutorial with movies & nice
graphics
http://chem.lapeer.org/Chem1Docs/ElementQuiz.html online elements quiz
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More Sites about atoms:
The Atom - Succeed in Physical Science
http://lpmpjogja.diknas.go.id/kc/a/atom/atom.htm
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