Atoms and the Periodic Table

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Atoms and the Periodic Table
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• Chemists used the properties of elements to sort
  the elements into groups.
• Mendeleev used increasing atomic mass to
  construct his table.
• He knew some elements had similar chemical and
  physical properties!
• He put each element on a card with its melting
  point (MP) density, color, atomic mass and the
  of bonds it would form.
• He was able to predict undiscovered elements and
  their properties after he arranged the cards by
  atomic mass!!
• Modern periodic table has elements arranged in
  increasing atomic number (we needed to identify
  subatomic particles before we could use atomic )

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• When Mendeleev arranged his cards of elements he
  noticed that the pattern was not quite right, but
  when he moved a few cards over and left spaces
  the pattern worked. He concluded that the spaces
  were yet undiscovered elements. He was able to
  predict the properties of these elements!
• Today the periodic table looks a little
  different, more elements have been found and we
  have discovered sub atomic particles which
  allowed scientists to re arrange the elements by
  atomic number. The pattern became even more
  regular!

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Atomic number.
Atomic symbol
6 C Carbon 12.011
Element name
Average atomic mass -
Review To find the number of protons, see the
atomic number. To find the number of electrons
(see the atomic number) To find the number of
neutrons, subtract the atomic number from the
atomic mass. Use whole number. Atomic mass --
12 Atomic - 6
6
neutrons
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V. How Do The Structures of the Atoms Differ? A.
Atomic Number - of protons in the nucleus 1.
Also tells the number of electrons in a neutral
atom 2. Each atom has a unique atomic number
never changes 3. It identifies the atom 4.
Usually the smallest number, always a whole B.
Mass Number sum of the protons neutrons 1.
Usually the biggest number, often a decimal C.
Ion an atom or group of atoms that has lost or
gained 1 or more electrons therefore has a net
(overall) charge D. Isotope atoms of the
element with different numbers of neutrons Ex
C-12 and C-14 E. Average Atomic Mass weighed
average mass of a elements isotopes why the mass
is usually not a whole number
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• I Organization of the Periodic Table
• A. Elements are arranged based upon atomic number
  ( of protons). Usually the smallest of the 2
  numbers
• Periodic Law when elements are arranged the way
  there are because of similarities in properties
  and it occurs in a regular pattern.
• B. Period (series) horizontal rows
• Number of protons and electrons increase by 1 as
  you move across a period.
• C. Group (family) vertical columns
• Elements in these groups have the same number of
  valence electrons and have similar properties

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Because the first shell is full at 2 it is at the
end of the period,
instead of in the second group with the other
elements with 2 valence electrons
Groups Or families
Periods
(when we write a sentence, we go ACROSS the paper
and put a PERIOD at the end.)
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Group 6 Gains 2 -e
Group 7 -1 Gains 1 -e
Group 2 2 Looses 2 -e
Group 4
Group 5 -3 Gains 3 -e
Group 3 3 Looses 3 -e
Group 8 No charge
Group 1 1 Looses 1 -e
If you gain an electron e- you increase your (-)
charge
Less (electrons) is more () of a charge
Transition metals Variable charges
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How Are Elements Classified

• Nonmetals (except H) are found on the right side
  of the chart. They may be solid, liquid or
  gassolid ones are usually dull,brittle (shatter
  if hit with a hamer)
• Form (-) ions.
• They are poor conductors of electricity except
  for C
• Metalloids (semimetals) have properties of both
  metals and nonmetals. Ex Boron, Silicon,
  Germanium, Arsenic, Antimony and Tellurium

• Metals are usually shiny solids that can be
  stretched and shaped
• They are ductile (put into thin wire) and
  malleable( hammered into sheets).
• They are also good conductors of heat and
  electricity.
• Most of the elements are metals.
• They are on the left side of the periodic table
• Form () ions

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Alkali Metals - Group 1

• Soft, shiny metals that react violently with
  water and other stuff.
• 1 valence electron in this groupvery reactive.
  Will give up an electron.
• Form 1 ion
• Ex. Sodium reacts quickly with Cl to give up an
  electron to it and become NaCl, salt.
• Must store in oil

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Alkaline Earth Metals- Group 2

• Have two valence electrons, are not as reactive
  as alkali metals, but still reactive enough to
  form 2 ions and react to form compounds.
• Calcium forms many hard compounds used to
  strengthen organic structures shells become
  limestone and marble, coral and bones and teeth.
• Magnesium- light structural material, milk of
  magnesia, Epsom salts, and flares.

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Transition metals

• Much less reactive, but still can forms ions.
  Transition metals can be 2, 3 and even 4
• Many times you will know the charge because of
  Roman Numerals in () s
• Ex Cu (III) is Copper with a 3 charge

Mercury- on metal that is liquid at room temp
useful in thermometers and thermostats, but has
been replaced due to toxicity. Gold, Silver,
Platinum- very shinyjewelry use.
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Other Nonmetals

• Group 3 Boron group. These have 3 charge and
  have 3 valence electrons Ex Aluminum (Al)
• Group 4 Carbon group. These have -4 charge and
  have 4 valence electrons Ex Carbon (C) pure
  state is found as graphite and diamonds.
• Group 5 Nitrogen group. These have -3 charge
  and have 5 valence electrons Ex Nitrogen 75 of
  air is made of nitrogen

• Group 6 Oxygen group. These have -2 charge and
  have 6 valence electrons. Ex Oxygen 20 of air
  is made of oxygen. Sulfur yellow, odorless
  solid, in compounds give off a terrible smell

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Halogens - Group 7

• 7 valence electrons and have a (-1) charge
• Very reactive especially with group 1
• Ex Bromine (Br) only liquid nonmetal at room
  temp
• Ex Fluorine (Fl) used in toothpaste
• Ex Chlorine (Cl) used in swimming pools

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Nobel gases - Group 8

• All gases. Different from most elements, because
  they are very unreactive.
• 8 valence electrons, so they wont react with any
  other elements.
• Also known as inert.
• Ex Neon (Ne) - used in neon signs (mixed with
  other elements gives other colors).
• Ex Helium (He) - is very light (used in
  balloons).
• Ex Argon (Ar) - used in light bulbs to prevent
  it from burning up

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2 He
This group, the Noble gases (group18) is usually
very unreactive. This is because they all have
full valence electron shells. Helium (He) has 2e
in the 1st shell (holds 2), Neon (Ne) has 2e in
the lst shell, and 8e in the 2nd shell (full).
10 Ne
18 Ar
36 Kr
54 Xe
86 Rn