Ch 3 Atoms and Periodic Table Notes

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Ch 3 Atoms and Periodic Table Notes

• Vocab nucleus, proton, neutron, electron, Energy
  level, orbital, Valence electron, Periodic law,
  Period, Group, Ionization, Ion, Cation, Anion,
  Atomic number, Atomic mass number, Isotopes,
  Atomic mass unit, Average atomic mass, Metals,
  Nonmetals, Semiconductors, Alkali metals,
  Alkaline-earth metals, Transition metals,
  Halogens, Noble gases

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3.1 Atomic Structure

• What gives different matter distinct properties?
• - the atoms in that type of matter
• Atoms are tiny units that determine properties of
  matter
• - each element has its own atom

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Daltons Atomic Theory 1808 English
schoolteacher

• Every element is made of tiny particles called
  atoms that cant be divided.
• Atoms of the same element are exactly alike.
• Atoms of different elements can join to form
  molecules.
• - We have since learned that atoms can be divided.

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Atomic Structure

• Nucleus center of atom
• Protons neutrons
• Overall positive charge

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• Electron Cloud surrounds nucleus
• Contains space where electrons are found
• Overall negative charge
• Overall positive and negative attraction keeps
  electron cloud close to the Nucleus

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Sub-Atomic Particles

• Proton charged molecule in nucleus
• Written as p
• Mass of 1.67 x 10-27
• Neutron a neutral particle in nucleus (NO
  charge)
• Written as n
• Mass of 1.67 x 10-27

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• Electron a - charged particle moving around
  the outside of nucleus in an electron cloud
  think of fan blades
• Written as e-
• Mass of 9.11 x 10-31. Very little mass
• Atoms have no overall charge because they have an
  equal number of protons and electrons.

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Electron Cloud Orbitals

• It is impossible to know the exact location of a
  given electron in its electron cloud.
• So we have a general area based on an electrons
  energy level. General rule the more energy an
  electron has, the farther from the nucleus and
  the positive protons it can get.

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• Orbitals a region in an atom where there is a
  high probability of finding electrons we only
  look at two types, there are more.
• S-orbitals are spherically shaped
• Holds first two electrons of every element
• Is the lowest energy level
• After 1st S-orbital is full, a second fills with
  2 more e-

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• P-orbitals are peanut shaped
• When the 2 s-orbitals are full (4e-), the 5th
  through 10th electrons will fill p-orbitals
• These electrons have slightly more energy than
  the first 4

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Electron Clouds and Energy

• Electrons move about the electron clouds
  (orbitals) based on their energy levels.
• Analogy sun and planets

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• General Atomic Model
• 1st energy level
• s-orbital with 2e-
• 2nd energy level
• s-orbital with 2e-
• 3 p-orbitals with 2e- each 6e-

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• Valence electron an electron in the outermost
  energy level of an atom
• hydrogen has 1 helium has 2 lithium has 1
• these are the electrons that will allow the atom
  to react with others

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3-2 A Guided Tour of the Periodic Table

• The periodic table is a visual representation of
  the elements organized by properties.
• Each element has a symbol
• Organized by of protons also called the atomic
  number

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• Periodic law properties of elements tend to
  change in a regular pattern when elements are
  arranged in order of increasing atomic number, or
  number of protons in their atoms.

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History of the periodic table

• Dmitri Mendeleev (1834-1907)
• Organized 70 known elements into a able according
  to common characteristics.
• Problem ? there were many empty spaces and it was
  very long

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• Henry Moseley (1887-1915)
• Determined the atomic number of elements and
  recognized Mendeleevs table to what we know today

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The Periodic Table

• Periods are horizontal rows
• There are 7 periods
• The protons and electrons increases from left
  to right
• Other properties also follow pattern including
  size of molecule

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• Groups are vertical columns
• Also called families because elements in the same
  group share physical and chemical properties.
• Elements in a group have the same of valence
  electrons
• Each group is identified by a number and letter

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Ions

• Atoms that do not have a filled outermost energy
  level may undergo a process called ionization.
• The atom will either gain or lose valence
  electrons.
• Example Element Lithium from Group 1 is very
  reactive. Li will give away its 3rd electron and
  become a positive ion.

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• All elements in the first group on the periodic
  table will react the same way
• A positive ion is called a cation
• A negative ion is called an anion

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• Each element and its information can be found in
  a box on the periodic table.
• General format

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• Atomic number
• Is equal to the number of protons in the nucleus
• Will also equal the number of electrons in the
  electron cloud
• Will always be a whole number on the table (no
  decimals)

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• Atomic mass
• The mass of the nucleus of the atom
• The combined number of protons AND neutrons in an
  atom
• Atomic mass p n
• Will always be the larger number

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• Protons
• Electrons
• Neutrons
• Protons
• Electrons
• Neutrons

8 Oxygen 16
12 Carbon 6
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• Protons
• Electrons
• Neutrons
• Protons
• Electrons
• Neutrons

4 Helium 2
5 Boron 11
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Isotopes

• Different versions of an element that have
  different numbers of neutrons.
• They have the same protons, but different masses

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• This is why the average atomic masses on the
  periodic tables are decimals, the mass is a
  combination of all isotopes.
• Ex Hydrogen has 1p, 1e-, and has a mass of
  1.007 because it is mostly found as an isotope
  with no neutron

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The mass of an atom

• It is very small, so they decided to measure a
  Carbon-12 atom (6 protons and 6 neutrons) and
  divide into 12 meaning they said each proton and
  neutron equals 1 atomic mass unit

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3-3 Families of Elements

• - How are elements classified?
• Metals versus Nonmetals
• Most elements are metals
• Most metals are shiny solids that can be
  stretched and shaped
• They are good conductors of heat and electricity

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• Nonmetals are usually on the right of the
  periodic table
• Include solids, liquids and gases
• Nonmetal solids are usually poor conductors of
  heat and electricity
• Some can conduct under certain conditions
  semiconductors

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The Periodic Table

• Metals There are 4 different groups

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Alkali Metals - Group 1 (except hydrogen)

• Soft and shiny
• Have one valence electron forms
• cations very easily
• React violently with water elements are usually
  stored in oil
• Only found in compounds in nature
• video

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Alkaline Earth Metals Group 2

• Have 2 valence electrons
• May react to form ions with 2 charge
• Calcium is very important in skeletons
• Magnesium is the lightest structural material

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Transition Metals Groups 3-12

• May lose electrons to form multiple cations
• All conduct heat and electricity
• Copper wire
• Can be stretched and shaped without breaking
  gold and silver jewelry

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Synthetic Elements

• Some of the transition metals are man-made
  Tc-43, Pm-61 and Atomic numbers 93 and above
• Many are radioactive the nuclei are continually
  decaying to produce different elements

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Nonmetals all but Hydrogen are found on the
right of P. Table

• Carbon is a very important non-metal
• Pure state graphite, pencil lead
• Diamond
• In body structure

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Halogens Group 17

• Very reactive gain electron to form -1 anions
• Chlorine is used to kill bacteria pools,
  drinking water
• Fluorine anion prevents tooth decay

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Nobel Gases Group 18

• Exist as single atoms because they are inert or
  unreactive the outer energy level is full of
  electrons
• Neon is used in neon signs
• Helium is less dense than air it floats

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Semiconductors or metalloids 6 elements

• Have some properties of metals
• Under certain conditions, they can conduct heat
  and electricity
• Silicon is very important in modern technology