Ch 5.2: Electron configuration and the periodic table.

1
Ch 5.2 Electron configuration and the periodic
table.
2

• In general terms, the electron configuration of
  an atoms highest occupied energy level
  determines the atoms chemical properties.

3
Periods and Groups

• Elements are arranged vertically in groups that
  share similar chemical properties.

4
Periods and Groups

• Elements are arranged horizontally in periods
• the length of each period is determined by the
  number of electrons that can occupy the sublevels
  being filled in that period.

5
Sublevel Blocks

• Based on the electron configuration of the
  elements, the periodic table can be subdivided
  into four sublevels, or blocks.

6
Alkali Metals Group 1 ( ns1)

• Most reactive, soft, silvery metals.
• Stored under kerosene/oil.
• Are not found free in nature, but as compounds -
  too reactive to exist alone.
• Combine readily with non metals.
• Combine readily with water
• 2 H2O 2 X ? H2 2 XOH
• Melting point decreases as you move down the
  group.

Group configuration
7
Alkaline Earth metals Group 2 (ns2)

• Barium in oil.

• Similar to group 1, but are harder, denser,
  stronger, and have higher melting points.
• Less reactive than the alkali metals, but still
  too reactive to be found free in nature.

8
Special Cases H and He

• By electron configuration H is in Group 1, but it
  does not have the characteristics of an alkali
  metal.
• By electron configuration He should be in Group
  2, but it does not have the chemical
  characteristics of the group and acts as a noble
  gas, so it is put in Group 18.

9
Example 1

• Without looking at the periodic table, give the
  group, period, and block in which the element
  with the electron configuration Xe6s2 is
  located.
• Group 2 (ns2)
• Period 6 (6s2)
• Block s (6s2)

10
Example 2

• Without looking at the periodic table, write the
  electron configuration for the Group 1 element in
  the third period.
• 1s22s22p63s1

11
Example 2

• Which element is likely to be more active
• Xe6s2 or 1s22s22p63s1 ?
• 1s22s22p63s1 because it is in Group 1 (alkali
  metals)

12
Example 3

• Without looking at the periodic table, give the
  group, period, and block in which the element
  with the electron configuration Kr5s1 is
  located.
• Group 1 (ns1)
• Period 5 (5s1)
• Block s (5s1)

13
Example 4

• Without looking at the periodic table, write both
  the group configuration and the complete electron
  configuration for the Group2 element in the 4th
  period.
• Group ns2
• 1s22s22p63s23p64s2

14
Transition metals (d block) Groups 3-12

• Sum of d and s electrons give group number of the
  element. Ex. Cr Ar 4s13d5 is in group 6.
• Metallic properties (shiny, conduct heat and
  electricity, ductile, malleable)
• ns2(n-1)dx

15
Transition Metals

• are less reactive than Groups 1 and 2
• Some are so unreactive that they do not easily
  form compounds and can exist in nature as free
  elements (also called native elements).

Native gold
16
Example 4

• An element has the electron configuration
  Kr5s24d10 Without looking at the periodic
  table, identify the period, block, and group in
  which this element is located.
• Period 5 (5s2)
• Block d (5s24d10)
• Group 12 (210)

17
P block elements Group 13-18

• The p-block elements together with the s-block
  elements are called the main group elements.
• The properties of the elements in the p block
  vary greatly (mixture of metals, metalloids,
  non-metals, and the noble gases).
• (ns2np1 through ns2np6)
• Group number ns electrons np electrons 10

18
P block elements Group 13-18

• Metalloids Brittle solids, semiconductors,
  exhibit properties of both nonmetals and metals.
• P-block metals less dense and hard than d-block
  metals, but greater than Groups 1 and 2. When
  pure, are stable in the presence of air.
• Noble gasesunreactive. Why????

19
Group 17 The Halogens

• Halogens most reactive nonmetals
• React vigorously with metals, forming salts.
• F2 (green gas), Cl2 (yellow gas), Br2 (red
  liquid), I2 (purple solid).
• (ns2np5)

20
Group 18 - Noble Gases

• Stable elements, do not normally undergo chemical
  reactions.
• The stability is a result of electrons filling
  the highest energy level.
• Helium is 1s2, all the other noble gases are said
  to have stable octets because the configuration
  is ns2 np6 (8 electrons in outer energy level
  octet).
• (ns2np6)

21
Lanthanides (Rare Earths)

• Shiny, reactive metals.
• Similar in reactivity to the Group 2 alkaline
  earth metals.
• Electrons fill up f orbitals.
• Atomic 58-71

22
Actinides

• All radioactive metals.
• First 4 naturally occurring.
• The remainder are called the transuranic elements
  (beyond uranium), and are synthesized
• Atomic 90-103

23
Example 5

• An element has the electron configuration
  Ne3s23p5 Without looking at the periodic
  table, identify the block, and group in which
  this element is located.
• Block p (3s23p5)
• Group 17 (2510)

24
Example 6

• An element has the electron configuration
  Ne3s23p5 What element is this? Is this a
  metal, nonmetal, or metalloid?
• Chlorine
• Group 17 halogen (non-metal), which means it is
  very reactive.

25
Example 6

• An element has the electron configuration
  Xe6s24f6 What element is this? Is this a
  metal, nonmetal, or metalloid?
• This is an f-block element in the lanthanides
  (4f). Samarium, Sm.
• Lanthanides are reactive metals.

26
Assignment Due tomorrow

• 5.2 Worksheet

Yee-hah!!!