Atomic Structure and the Periodic Table

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Atomic Structure and the Periodic Table
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All Matter is Made of Atoms

• Hydrogen is the most common atom of our universe
• Types of atoms in Earths Crust
• Iron 5, Aluminum 8, Silicon 28, Oxygen 47,
  Other 12
• Types of atoms in Humans
• Nitrogen 3, Hydrogen 10, Oxygen 61, Other 26

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Names and Symbols of Elements

• Each element has its own symbol
• Some elements use the first letter of the name
  hydrogen (H), Sulfur (S),Carbon (C)
• Other elements use the first letter of the name
  plus another letter aluminum (Al), Platinum
  (Pt), Zinc (Zn)
• The first letter is always capitalized and the
  following letters are lower case.

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400 B.C.
Early Greek Philosophers determined that atoms
are the building blocks of matter.
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John Dalton (17661844)

• John Daltons theory of the atom started out as a
  solid sphere with no charges
• Proposed the atomic theory by investigating
  atomic weights of atoms

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1898-1903
J.J. Thomson determines that an atom is made up
of negative electrons embedded in a sea of
positive charges .
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1911
Ernest Rutherford did some experiments with thin
metal foils and found that the positive charge is
located within a central nucleus
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1913
Neils Bohr worked under Rutherford but found
problems with his theory. He ultimately
determined that Electrons are in circular orbits
with increasing energy levels.
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The modern atomic model shows that electrons
occupy regions of space whose shape is described
by complex mathematical equations. (James
Chadwick)
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History of Atomic Theory

• John Daltons theory of the atom started out as a
  solid sphere with no charges.
• Then J.J. Thomson figured out there were positive
  and negative charges in an atom.
• Rutherford determined that the positive charges
  (protons) were located in the center of the atom
  and the negative charges (electrons) were
  scattered around the nucleus
• Bohrs theory said that the protons are in the
  middle and the electrons travel in specific
  energy levels and orbits around the nucleus
• Modern model- protons and neutrons in nucleus,
  electrons on energy levels

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Review

• An atom is made up of protons (),
• neutrons (no charge), and electrons(-).
• The protons and neutrons are found in the nucleus
• There has to be an equal number of protons and
  electrons because atoms have no net charge!
• Atomic mass is the number of protons and neutrons
• Atomic number is the number of protons (which is
  the same as the number of electrons)

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Vocabulary

• Atom the smallest particle of an element that
  has the chemical properties of the element
• Nucleus found in the center of the atom and
  contains the protons and neutrons
• Proton a positively charged particle found in
  the nucleus of an atom
• Neutrons an uncharged particle found in the
  nucleus of an atom
• Electron negatively charged particles that move
  around outside the nucleus of the atom
• Isotopes atoms of the same element that have a
  different number of neutrons. Chlorine atoms
  have 17 protons, but some atoms of chlorine have
  18 or 20 neutrons these atoms are the isotopes of
  chlorine

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Atoms form Ions

• Ions formed when an atom loses or gains one or
  more electrons(- or charge)
• Cation formed when an atom loses an electron (
  charge)
• Anion formed when an atom gains an electron
  (-charge)

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Elements are organized by similarity

• Modern Periodic Table organized by the atomic
  of the elements
• Dmitri Mendeleev began organizing elements by
  their physical and chemical properties (1860s)

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Periodic Table of the Elements

• Mendeleev produced the first periodic table
• Called the periodic table because a periodic, or
  repeating pattern of properties of the elements

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Periodic Table

• Period each row of the periodic table is called
  a period. If you read from left to right one
  proton and one electron are added from one
  element to the next
• Group/Family Each column of the table is called
  a group or family. Elements in a group share
  similar properties. Groups/Families are read from
  top to bottom

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Atomic Size on the Periodic Table

• Left to right atomic size decreases
• Top to bottom atomic size increases

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More Properties of Periodic Table
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Periodic Table has distinct regions

• Reactive indicates how likely an element is to
  undergo a chemical change
• Most elements are somewhat reactive and combine
  with other materials
• The most reactive are in groups (up/down) 1 and
  17
• The least reactive are in group (up/down) 18

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Elements combine by the outside electrons

• All of the electrons in the combining elements do
  not interact with each other to form compounds.
• Valence Electrons Only the electrons in the
  elements outside energy level interact with each
  other.
• The most stable configuration has 8 electrons in
  the outer energy level.
• Elements in group 1 have 1 electron in outside
  energy level and elements in group 17 have 7
  electrons in outside energy level so they react
  with each other easily to form compounds and
  fulfill the 8 electron stable configuration.

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Metals

• Most elements are metals
• Metals are elements that conduct electricity and
  heat, have shiny appearance, and can be shaped by
  pounding (malleability), bending, or being drawn
  into a thin wire (ductility)

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Metal types

• Reactive metals Group (up/down) 1 most reactive
• Transition Metals Group 3-12 (up/down) generally
  less reactive than most metals

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Rare Earth Elements
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• Top row of the two rows of metals that are
  outside of the main periodic table
• Also known as Lanthanides because they follow the
  element lanthanum (La) on the table
• Scientists once thought these metals were
  available only in tiny amounts on the Earth

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Actinide

• bottom row of the two rows of metals that are
  outside of the main periodic table
• The Actinide series is all radioactive and some
  are not found in nature.

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Nonmetals

• Nonmetals the elements on the right side of the
  periodic table
• Many are gases at room temperature, dull surfaces
  on the solid nonmetals, cannot be shaped by
  ductility or malleability

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Halogens

• Elements in group 17
• 7 valence electrons
• Greek forming salts
• Very reactive non-metals that easily form
  compounds with metals. These compounds are known
  as salts.

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Noble Gases

• Group 18 on the periodic table
• 8 valence electrons
• Noble or inert because they almost never react
  with other elements

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Metalloids

• Have properties of both metals and nonmetals
• Located on either side of the zigzag line
  separating metals and nonmetals
• Most common is Silicon

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Radioactivity

• Radioactivity the process by which the nucleus
  of an atom releases energy and particles
• Marie Curie was the first person to isolate two
  radioactive elements (polonium and radium)
• An isotope is radioactive if the nucleus has too
  many or too few neutrons

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Radioactive Decay

• Radioactive atoms produce energy and particles
  from their nuclei
• The identity of these atoms changes because the
  of protons changes. (radioactive decay)
• Occurs at a steady rate characteristic to each
  isotope
• The amount of time for one-half of the atoms to
  decay is called the half-life of the isotope

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Radioactive Decay

• Parent decays into daughter isotope.
• Combination of both is 100
• Parent starts at 100 and decays to 50
• 100 1 half-life to 50 (daughter 50)
• 50 2 half-lives to 25 (daughter 75)
• 25 3 half-lives to 12.5 (daughter 87.5)
• 12.5 4 half-lives to 6.25 (daughter 93.75)