Using the Periodic Table

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(No Transcript)
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Chemical Symbols in the Periodic Table
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How is the Periodic Table Arranged?

1. Alphabetically from A to Z
2. By atomic mass, from small to large
3. By number of protons, starting with 1
4. Randomly
5. In the order the elements were discovered

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Periodic table is arranged by number of protons!

• This is also by Atomic Number
• By coincidence, the elements are generally in
  order of increasing atomic mass, but not
  always..

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For example.

• Cobalt has 27 protons, mass 58.9 amu
• Next after Co comes Nickel
• Nickel has 28 protons , but mass 58.7 amu (less
  mass than cobalt)

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Periods

• Periods are the horizontal rows. There are 7
  periods

1
2
3
4
5
6
7
(6)
(7)
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Groups or Families

• Groups (also called families) are the vertical
  columns. There are 18 groups.

1
18
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Most elements are metals
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Non-metals live in upper right corner (except
Hydrogen)
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6 Metalloids live near the red stairB, Si, Ge,
As, Sb, Te
X
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Group 1 metals are called alkali metals
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Group 2 metals are called alkaline earth metals
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Transition Metals are in groups 3 through 12They
tend to form colorful ions and compounds
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Halogens are in group 17 Noble
gases in group 18
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7 elements are DIATOMIC
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Allotropes

• Elements that can exist in different forms in the
  same phase are allotropes
• O2 (oxygen gas) and O3 (ozone) are allotropes
• Allotropes have different chemical and physical
  properties

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Valence Electrons

• Definition all the electrons in an atoms
• HIGHEST ENERGY LEVEL

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Valence Electrons

• Remember There are seven energy levels
• Energy Level 1 can hold two e- in S orbital
• Energy Level 2 can hold two e- in S, 6 in P
• Energy Level 3 S, P, D
• Energy Level 4-7 S, P, D, F

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However.

• Since according to the aufbau principle d and f
  orbitals fill after the S and P orbitals in the
  next highest energy level,
• Valence electrons are always in S or P orbitals
• (2 in S) (6 in P) 8 (max) Valence e-

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How to determine which e- are valence e-

• Step 1 Write out the electron configuration for
  the atom
• 11Na 1S2 2S2 2P6 3S1
• Step 2 Count how many e- in the highest energy
  level
• Energy level 3 highest, so there is 1 valence e-

Level 3 is highest
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The good news

• It is easy to determine valence e- simply by
  looking at the periodic table
• Group 1 has 1 valence e-
• Group 2 has 2
• Group 13 has 3
• Group 14 has 4
• Group 15 has 5.. Group 18 has 8

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What about the transition metals?

• For now, assume that they have 2.
• But sometimes they can also have 1, or 3 or more

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Write out the e- configuration for the following
elements, then check and see what Group they are
in

• 12Mg
• 8O
• 17Cl
• 18Kr
• 26Fe
• 19K