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Chapter 5
Section 5.5 Electron Configurations
and the Periodic Table
Periodicity
 The reason for periodicity is the
arrangement of the electrons around the
nucleus of the atoms.
Periodic Table Vocabulary
(review and element song)
 Groups or families – ↕
 Periods or series - ↔
 Metals – left and center
 Stair step line – metalloids
 Nonmetals – right
 Semimetals or metalloids – on zig zag
line
Electron Configurations and
the Table
 Based on the electron configuration of
the elements, the periodic table can be
divided into 4 blocks: s, p, d, and f.
 Periods relate to principal energy levels,
n
 Groups relate to sublevels, l
s-block elements
 Group 1: alkali metals
 Electron configurations end in s1
 Soft silvery, reactive, not found in nature
as free elements
 “sodium a spectacular element” video
clip
 Hydrogen – unique properties
Group 2: Alkaline earth metals
 Electron configurations end in s2
 Harder, denser, and stronger than alkali
metals; less reactive than alkali metals,
but still too reactive to be found in nature
as elements
 Helium – first of the noble gases
p-block elements Groups 13-18 Electron
configurations end in p1 for group 13 and p6 for group 18
Group 17: halogens
 Electron configuration end in p5
 One electron short of noble gas (stable)
electron configuration
 Most reactive nonmetals
Group 18: Noble Gases
 Last to be discovered because of their inactivity
 Extremely stable configuration (end in p6)
*The 6 elements classified as metalloid are on
either side of the stair step line in the p-block
d-block elements
Group 3-12: Transition metals
 Electron configurations end in d1 for
group 3 and end in d10 for group 12
 Good conductors of heat and electricity
 Less reactive than s block metals
 Some exist in nature as free elements
f-block elements
Sometimes called the inner transition
metals
 electron configurations end in f1 and f14
 Lanthanides (58-71) follow lanthanum
(period 6)
 Actinides (90-103) follow actinium
(period 7) include manmade elements
past uranium