5'1 Organizing the Elements

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5.1 Organizing the Elements

• Mendeleevs Periodic Table

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A. Periodic Table History

• In the late 1700s, the discovery of new elements
  boomed.
• It became increasingly important to organize
  these newly discovered elements.

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A. Periodic Table History

• Early scientists put them in large groups didnt
  work for all elements!

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Triangular Periodic Table
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Mayan Periodic Table
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Spiral Periodic Table
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Stowe Periodic Table
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A. Periodic Table History

• Dmitri Mendeleev organized elements into a simple
  table with rows and columns
• First system that worked for all known
  elements!

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A. Periodic Table History

• Based his system on a card game

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A. Periodic Table History

• Lined element cards up by increasing atomic mass
  (L ? R and Top? Bottom)

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A. Periodic Table History

• Cards with similar chemical physical properties
  were placed in the same column

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A. Periodic Table History

• Left blanks for undiscovered elements

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A. Periodic Table History

• Predicted the properties of these elements would
  be similar to properties of other elements in the
  column.

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A. Periodic Table History

• The accuracy of his predictions caused others in
  the scientific
  community to accept his
  method of organization.

• Eka-Aluminum
• Predicted properties
• Soft metal
• Low melting point
• Density 5.9 g/cm3

• Gallium (discovered 1875)
• Actual properties
• Soft metal
• Low melting point
• Density 5.91 g/cm3

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Mendeleev Cards Activity

• Making a Model of the Periodic Table

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Think About It

• Notes on a keyboard repeat at regular octaves
  (8-note intervals).

Any regular, repeating pattern is called a
periodic pattern.
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B. Modern Periodic Table

• The modern periodic table is arranged by
  increasing atomic number.

Remember, protons had not been discovered when
Mendeleev created his table.
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B. Modern Periodic Table

• Periodic Law - properties of elements repeat from
  row to row when arranged by atomic .
• Horizontal rows periods
• Vertical columns groups
• (a.k.a. families due to
  shared properties within
  a column)

HINT There are 7 periods on the periodic table
and 7 periods in a school day at HSE
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B. Modern Periodic Table

• of elements in each period varies
• Higher energy levels can hold more electrons
  than lower energy levels

Period 1 2 elements 1st energy level holds 2
e- Periods 2 3 8 elements 2nd 3rd energy
levels hold 8 e- each Periods 4 5 18
elements 4th 5th energy levels hold 18 e- each
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C. Classifying Elements

• Solids, liquids gases (color coded font on PT
  handout)
• Natural (1-93) or man-made

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C. Classifying Elements

• Metals - left of stair step line
• Nonmetals - right of stair step
• Metalloids - touch stair step

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C. Classifying Elements

• Families of Elements

Alkali Metals Noble Gases Alkaline Earth Metals
Halogens Transition Metals Inner Transition
Metals
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D. Periodic Trends

• A valence electron is an e- in the outermost
  energy level of an atom.
• Elements in a group have similar properties
  because they have the same of valence e-s.
• Short cut of valence e- A Group number

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D. Periodic Trends

• Bohr model diagrams show the of electrons in
  each energy level of an atom.

Lithium-7 Atomic 3 Mass 7 of
p 3 of e 3 of n 4
e-
e-
Maximum e- Level 1 2e- Level 2 8e- Level
3 8e- Level 4 18e-
e-
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D. Periodic Trends

• Draw a Borh Model diagram for

Nitrogen-14 (N)
Calcium-40 (Ca)
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D. Periodic Trends

• Lewis Dot diagrams show the valence electrons
  only.

Li
B
S
Ne
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D. Periodic Trends

• The most stable elements have a full outer energy
  level (8 e-, or
  2 e- for He.

B
Li
S
Ne
Ne
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D. Periodic Trends

• Elements in a family/group share similar
  properties because they have the same number of
  valence electrons.

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D. Periodic Trends

• The Noble Gases are stable and unreactive because
  their outer energy level is full with 8 valence
  electrons (or 2 in the case of He)

Ne
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D. Periodic Trends

• The Halogens are the most reactive nonmetals
• Only one more valence e- is
  needed to be stable
• They will react with any
  element to get the last
  needed e-
• Get less reactive further
  down the group why?

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D. Periodic Trends

• The Alkali Metals are highly reactive metals
• Gain a stable e- configuration
  by losing one valence e-
• Rarely found alone in nature
• Get MORE reactive further
  down the group why?
• Brainiac Video

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D. Periodic Trends

• Atomic size trends
• Atoms get LARGER down a group (more energy
  levels)
• Atoms get SMALLER from left to right across a
  period (stronger nucleus)

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D. Periodic Trends
Cl has a stronger nucleus to pull e- in tight
Nas nucleus is weaker
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D. Periodic Trends

• Properties vary across a period because the
  electron configurations vary.