Download The Periodic law

THE PERIODIC LAW
Chapter 5
DMITRI MENDELEEV
 First person to create a periodic table
• Periodic: repeating in pattern
 Mendeleev organized elements by increasing atomic mass
 Grouped elements with similar properties
HENRY MOSELEY
 Arranged the periodic table by increasing atomic number
 Periodic Law: the physical & chemical properties of the elements
are periodic functions of their atomic numbers
• When elements are arranged by increasing atomic number, elements
with similar properties appear at regular intervals
MODERN PERIODIC TABLE
 An arrangement of the elements in order of their atomic numbers
so the elements with similar properties fall in the same column or
group
PERIODS
 Horizontal rows
 7 periods
PERIODS
 Length of the period is determined by the number of electrons
that can occupy the sublevels being filled by that period
Period
# Elements in
Period
Sublevels
1
2
1s
2
8
2s2p
3
8
3s3p
4
18
4s3d4p
5
18
5s4d5p
6
32
6s4f5d6p
7
32
7s5f6d7p
GROUPS
 Vertical columns
 18 groups
REGIONS OF THE
PERIODIC TABLE
COLORS ON THE PERIODIC
TABLE
 Indicate the state of matter at room temperature
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BLACK: solid
RED: gas
BLUE: liquid
WHITE: synthetic/man-made
BLOCKS
S-BLOCK
 Groups 1 & 2
 Reactive metals
 Notice:
• Li= [He]2s1
• Na= [Ne]3s1
 Group 1 (Alkali Metals) = ns1
 Group 2 (Alkaline Earth Metals) = ns2
HYDROGEN & HELIUM
 Special cases
 H = 1s1
• Does not share properties with group 1
 He = 1s2
• Part of group 18 because it’s first energy level is full with 2 e-s
• Chemically stable like the noble gases
P-BLOCK
 Groups 13-18 (except He)
 All contain 2 ns electrons
 Valence electrons = group # minus 10
• Ex. Group 17 minus 10 = 7 valence electrons
 Halogens (group 17): most reactive nonmetals because they are one
electron short of a full outer shell
 Noble gases (group 18): unreactive because they have a full outer shell
 Metalloids: semiconducting elements
MAIN-GROUP ELEMENTS
 s & p blocks
D-BLOCK
 d-block groups don’t necessarily have identical outer electron
configurations
 The sum of the outer s + d electrons = group #
• Ex. Group 10
Ni = [Ar]3d84s2
Pd = [Kr]4d105s0
Pt = [Xe]4f145d96s1
 Transition elements: d-block elements; metals with typical metallic
properties
F-BLOCK
 Lanthanides
 Actinides
 Involve filling 4f & 5f orbitals
PERIODIC/GROUP TRENDS
 As you go across a period or down a group, trends can be
observed in:
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Valence electrons
Atomic radii
Ionization energy
Electron affinity
Ionic radii
Electronegativity
VALENCE ELECTRONS
 Electrons available to be lost, gained, or shared in the formation
of chemical compounds
 Main-group elements: valence electrons are in the outermost s & p
sublevels
• Correspond with the group number minus the transition elements
• Ex. Group 1 = 1 valence electron
Group 13 = 3 valence electrons
VALENCE ELECTRONS
 Periodic Trend: as you go across a period, the # of valence
electrons increases by 1
 Group Trend: as you go down a group, the # of valence electrons
stays the same (for main-group elements)