Atoms and the Periodic Table

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Transcript Atoms and the Periodic Table

Atoms and the
Periodic Table
http://www.turbosquid.com/FullPreview/Index.cfm/ID/246735
http://gpc.edu/~pgore/PhysicalScience/atom-with-electrons.gif
Matter and Atoms
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Everything made of matter
Matter has mass and volume
Matter made of atoms
Atoms are building blocks of matter
Atoms cannot be chemically divided
(H bomb - atoms going through a nuclear rxn,
NOT a chemical rxn)
Most matter made of compounds
Matter, Atoms, Compounds
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Compound: made of 2 or more types of atoms
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Ex: water: H2O made of 2 hydrogen atoms and 1 oxygen
atom
Learn later how compounds form
Elements: basic substances of matter
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Element cannot be further broken down chemically
Atom: smallest unit of an element that has the properties of
the element
Ex: hydrogen is an element, hydrogen atom is smallest unit
of hydrogen you can find
Periodic Table of Elements
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Created by Dmitri Mendeleev
in 1869
He noticed pattern of
properties amongst elements
when placed in order of
atomic mass
This order made problems in
the pattern
Today periodic table
arranged by atomic number
This better reflects patterns
of properties
http://jscms.jrn.columbia.edu/cns/2006-04-18/fido-luxuriantflowinghair/mendeleev/asset_medium
Periodic Table of Elements
http://www.dayah.com/periodic/
Neon
Iodine
Iron
http://img.alibaba.com/photo/50296091/Iodine.jpg
http://www.geocities.jp/senribb/jewels/Sulfur.jpg
http://mineral.galleries.com/minerals/elements/iron/iron.jpg
Boron
Sodium
http://www.vanderkrogt.net/elements/images/sodium.jpg
http://www.oneillselectronicmuseum.com/page9.html
Sulfur
Copper
http://gwydir.demon.co.uk/jo/minerals/pix/copper1.
http://www.theodoregray.com/PeriodicTableDisplay/Samples/005.1/s9.JPG
Periodic Table of the Elements
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Named periodic table b/c it’s periodic
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Regular repeating pattern in its arrangement
Today it has many more elements than in
1869
New discoveries = new elements
Atom is smallest whole unit of element
Organization of Periodic Table
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Vertical column = family or group
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Elements in group have similar chemical and
physical properties
Horizontal row = period
Sides of table = main elements
Middle of table = transition elements
Organization of Periodic Table
Outline metals, nonmetals, metalloids (different colors)
http://www.solpass.org/6-8Science/8s/Standards/periodic%20table.JPG
Organization of Periodic Table
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Metals: solids (except mercury), ductile,
malleable, conduct electricity, can make an
alloy (combo of metals)
Nonmetals: some solids, some liquid, some
gas, most do not conduct electricity
Metalloids: along “staircase”, hard to classify,
properties of metal and nonmetal
Periodic Table
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Atomic symbol (ex. H =
hydrogen)
Atomic mass = number or
protons & neutrons
Atomic # = number of protons
Na = sodium, Na is 11 so 11
protons; 23 -11 = 12 so 12
neutrons
Atom electrically neutral (#
protons = # electrons)
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Ex Na has 11 protons and 11
electrons
http://education.jlab.org/glossary/atomicnumber.html
Periodic Table
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Row = period
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Period ends when highest energy level is full or 8
e-
Noble gases: stable electron config.,
inactive/inert,
Halogens: group #17, 7 valence e-, like to
gain 1 electron to be happy
Alkali metals: group #1, 1 valence electron,
usually lose it to be stable
Atoms and Electrons
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Atoms
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Nucleus w/ protons & neutrons
Electrons orbit nucleus
Bohr found electrons move
around nucleus
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Electron found in energy level
Each energy level has different
amount of energy
http://education.jlab.org/qa/atom_model_03.gif
Atoms & Electrons
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Each energy level can only hold specific number of
electrons
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Level 1: 2 eLevel 2: 8 eLevel 3: 18 eLevel 4-7: 32 e-
Valence electron: found in highest energy level
(shell)
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electrons loosely held by nucleus
Determine how atom reacts/bonds w/ another atom
Determine chemical properties & reactivity of element
Atoms and Electrons
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Core electrons: electrons found in inner
shells/energy levels
Valence electrons - occupy outermost shell/energy
level
Electrostatic force: bonding force that holds 2 or
more atoms together b/c electrons are rearranged
between the atoms
Main group elements: group number = number of
valence electrons
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Elements in same group have same number of valence eElements in same group have similar properties b/c same
valence e-
Atoms and Electrons
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Bohr model: shows number of
energy levels and number of
valence electrons
Doesn’t work for transition
elements (we will learn why
later)
Ex: Na (sodium) Group 1 so 1
valence eK (potassium) (draw model
out)
Sodium
http://homepages.ius.edu/GKIRCHNE/BohrNa.jpg
Atoms and Electrons
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Energy levels want to be full
If can’t be full - better to have 8 e- in shell to
be stable
8 e- in last shell = stable electron
configuration; less likely to react
Noble gases (group 18) 8 valence e- and
inert (do not react)
Ex. B (boron)
Ex. Calcium (Ca)
Stable Electron Configuration
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Full energy level = stable
8 e- in outer shell = stable
Atom can do 2 things to become stable
1) give away electrons in outer shell
 2) take electrons from other atoms who need to
give the electrons up to be stable
Gaining/Losing electrons to become stable allows
atoms to chemically react/bond w/ other atoms
Atoms must be stable to be happy!
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Periodic table and electrons
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Halogens: group #17, 7 valence e-, like to
gain 1 electron to be happy
Alkali metals: group #1, 1 valence electron,
usually lose it to be stable
Bonding
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Bonding has to do w/ valence eMetal: reactivity depends on gaining/losing
electrons
Depends on how tightly atom holds its
valence eEasier to gain or lose?
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Less than 4 valence - easier to lose, takes less
energy
5 or more valence - atom holds onto e- and gets
more from another atom to fill its shell and be
stable