The Why and How of Ions

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The Why and How of Ions
Featuring the Return of Bohr-Rutherford Diagrams
and the Periodic Table
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Bohr-Rutherford Diagrams

• Bohr-Rutherford diagrams (or simply Bohr
  diagrams) are used to show the arrangement of
  electrons in the atom, e.g.

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How To Draw Bohr Diagrams

1. Find your element on the periodic table.
2. Determine the number of electrons, which for a
   neutral atom is equal to the number of ?

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How To Draw Bohr Diagrams

1. Find your element on the periodic table.
2. Determine the number of electrons, which for a
   neutral atom is equal to the number of protons,
   which is equal to the ?

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How To Draw Bohr Diagrams

1. Find your element on the periodic table.
2. Determine the number of electrons, which for a
   neutral atom is equal to the number of protons,
   which is equal to the atomic number.

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How To Draw Bohr Diagrams

• 3) Determine which period (row) your element is
  in.
• Elements in the 1st period have one energy level
  or shell.
• Elements in the 2nd period have two, and so on.

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How To Draw Bohr Diagrams

• 4) Draw a nucleus with the element symbol (and
  optionally, the s of protons and neutrons)
  inside.
• 5) Draw the shells around the nucleus.
• Carbon is in the 2nd period, so it has two energy
  levels or shells.

C
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How To Draw Bohr Diagrams

• 6) Add the electrons.
• Carbon has 6 electrons.
• The first shell can only hold ?

C
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How To Draw Bohr Diagrams

• 6) Add the electrons.
• Carbon has 6 electrons.
• The first shell can only hold 2 electrons.

C
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How To Draw Bohr Diagrams

• You need to add 4 more so these go in the 2nd
  shell.
• The 2nd shell can hold up to ?

C
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How To Draw Bohr Diagrams

• You need to add 4 more so these go in the 2nd
  shell.
• The 2nd shell can hold up to 8 electrons the 3rd
  shell can hold 18, but the elements in the first
  few periods only use 8 electrons.

C
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How To Draw Bohr Diagrams

• 7) Check your work Count your electrons per
  shell and your total electrons!

C
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Bohr Diagrams Practice

• Try drawing Bohr diagram for each of the
  following elements on your own
• H
• He
• O
• Al
• Ne
• K

C
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Bohr Diagrams Practice

• Try drawing Bohr diagram for each of the
  following elements on your own
• H 1 electron
• He
• O
• Al
• Ne
• K

H
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Bohr Diagrams Practice

• Try drawing Bohr diagram for each of the
  following elements on your own
• H
• He - 2 electrons
• O
• Al
• Ne
• K

He
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Bohr Diagrams Practice

• Try drawing Bohr diagram for each of the
  following elements on your own
• H
• He
• O - 8 electrons
• Al
• Ne
• K

O
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Bohr Diagrams Practice

• Try drawing Bohr diagram for each of the
  following elements on your own
• H
• He
• O
• Al - 13 electrons
• Ne
• K

Al
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Bohr Diagrams Practice

• Try drawing Bohr diagram for each of the
  following elements on your own
• H
• He
• O
• Al
• Ne - 10 electrons
• K

Ne
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Bohr Diagrams Practice

• Try drawing Bohr diagram for each of the
  following elements on your own
• H
• He
• O
• Al
• Ne
• K - 19 electrons

K
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Lewis Dot Diagrams

• The electrons in the outermost shell are called ?

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Lewis Dot Diagrams

• The electrons in the outermost shell are called
  valence electrons.

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Lewis Dot Diagrams

• The electrons in the outermost shell are called
  valence electrons.
• Lewis Dot Diagrams are abbreviated Bohr Diagrams
  that show just these outermost electrons, e.g.

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Valence Electrons and Families

• Note that both hydrogen (H) and potassium (K)
  have just ? electron in their outermost shell.
• Note also that these elements are both found in
  the ? column of the periodic table.
• This is not a coincidence!

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Valence Electrons and Families

• Note that both hydrogen (H) and potassium (K)
  have just 1 electron in their outermost shell.
• Note also that these elements are both found in
  the ? column of the periodic table.
• This is not a coincidence!

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Valence Electrons and Groups

• Note that both hydrogen (H) and potassium (K)
  have just 1 electron in their outermost shell.
• Note also that these elements are both found in
  the 1st column of the periodic table.
• This is not a coincidence!

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Valence Electrons and Groups

• All elements in the same group (column) have the
  same number of electrons in their outermost
  shell.
• It is these electrons that determine the behavior
  of the element, including how it reacts with
  other elements and how it forms ions.

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Valence Electrons and Groups

• Lets look at these groups or families in more
  detail. . . .

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ALKALI METALS

• 1 valence electron
• (Hydrogen is not officially a member)
• Soft and silvery metals
• Very reactive, esp. with water

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ALKALINE EARTH METALS

• 2 valence electrons
• White and malleable
• Reactive, but less so

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TRANSITION METALS

• (the Groups in the middle)

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BORON FAMILY

• 3 valence electrons
• Most are metals
• Boron is a metalloid.

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CARBON FAMILY

• 4 valence electrons
• Contains metals, metalloids, and a non-metal
  carbon (C)

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NITROGEN FAMILY

• 5 valence electrons
• Contains metals, metalloids, and non-metals

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OXYGEN FAMILY

• 6 valence electrons
• Mostly non-metals
• Reactive

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Halogens

• 7 valence electrons
• All are non-metals
• Very reactive

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Noble Gases

• Full outer shell
• Exist as gases
• Not reactive with other elements
• Do not form ions.

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The Why of Ions

• The Noble Gases do not react and do not form ions
  because they already have what all atoms want
  full outer shells.

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The How of Ions

• Atoms will either gain electrons to fill their
  outer shell (as in the case of the non-metal
  chlorine)

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The How of Ions

• or lose electrons to go down to their last full
  shell (as in the case of the metal sodium)

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Tune in next time. . . .

• More details on the formation of ions will be
  revealed tomorrow.