the periodic table -...
TRANSCRIPT
THE PERIODIC TABLE
Chapter 4
HOW ARE ELEMENTS ORGANIZED?
Groups of elements share certain properties
PERIODIC PATTERN
Newlands (1865) – Arranged elements
according to increasing atomic mass
Properties repeated every 8 elements
Law of octaves
Dobereiner (early 1800s)
Groups of 3 elements have similar properties
Triads
MENDELEEV
First periodic table
63 known elements at the time
Mendeleev’s table contains gaps that unknown elements should fill
He predicted the properties of these unknown elements & gave them names
MOSELEY
Arranged elements according to atomic number
Erased the discrepancies in Mendeleev’s table
OTHER CONTRIBUTIONS
Seaborg – pulled out inner transition elements
to condense periodic table
Ramsey – discovered noble gases
PERIODIC LAW
Elements with similar properties appear at
regular intervals (when arranged by atomic #)
Valence electrons – outermost electrons in an
atom of an element
Electrons that participate in chemical reactions
with other atoms
GROUPS/FAMILIES & PERIODS
Group/family = vertical column on the periodic
table
Elements have similar chemical properties because
of same # of valence electrons
Period = horizontal row
Elements have same number of occupied energy
levels (i.e. energy level 2)
GROUPS AND PERIODS
THE PERIODIC TABLE
Main Group elements
Transition elements
Inner transition elements
METALS, NONMETALS, METALLOIDS
Metals – occupy the majority of the periodic table
Located to the left of the “staircase”
Lustrous, Malleable, Ductile, Conductors
Alloy = a solid or liquid mixture of 2 or more metals
Nonmetals – generally opposite properties of metals
Metalloids – have properties of both, located along the “staircase”
METALS, NONMETALS, METALLOIDS
TRANSITION METALS
d-block elements
Groups 3-12
Do NOT have identical outer electron
configurations
May lose different #’s of valence electrons
Good conductors, ductile, malleable
LANTHANIDE & ACTINIDE SERIES
f-block elements
Lanthanides – first row of inner transition
elements
Shiny metals, similar in reactivity to alkaline earth
metals
Actinides – second row
Radioactive
ns
1
ns
2
ns
2n
p1
ns
2n
p2
ns
2n
p3
ns
2n
p4
ns
2n
p5
ns
2n
p6
d1
d5
d1
0
4f
5f
Ground State Electron Configurations of the Elements
ALKALI METALS – GROUP 1A (GROUP 1)
React with water to make alkaline solutions
One valence electron = VERY reactive
Lose their 1 valence electron to achieve noble gas configuration (octet)
Soft texture, dull or shiny, good conductors
Group 1A Elements (ns1, n 2)
ALKALINE EARTH METALS – GROUP 2A (GROUP
2)
Highly reactive
2 valence electrons
Harder and have higher melting points than
alkali metals
Group 2A Elements (ns2, n 2)
COMMON GROUP ELEMENTS – 3A TO 5A
(GROUPS 13-15)
3, 4, or 5 valence electrons (depending on group)
Some metals, some metalloids, some nonmetals
Group 3A Elements (ns2np1, n 2)
Group 4A Elements (ns2np2, n 2)
Group 5A Elements (ns2np3, n 2)
CHALCOGENS – GROUP 6A (GROUP 16)
Oxygen group
6 valence electrons
Name means “ore former”
Nonmetals, metalloids, metals
Group 6A Elements (ns2np4, n 2)
HALOGENS – GROUP 7A (GROUP 17)
Highly reactive nonmetals
7 valence electrons (1 short of a noble gas
configuration)
Often react with alkali metals
“Salt maker”
Group 7A Elements (ns2np5, n 2)
NOBLE GASES – GROUP 8A (GROUP 18)
Inert = unreactive
8 valence electrons (full set); except He (2 e-)
HYDROGEN
Most common element in
the universe
1 electron
Extremely flammable
Reacts unlike any other
element
PERIODIC TRENDS
Predictable change in a particular direction
Reactivity of Alkali metals
Increases as you down the group
Reactivity of Halogens
Increases as you go up the group
IONIZATION ENERGY
Energy supplied to remove an electron
IE + X (g) X+(g) + e-
Filled n=1 shell
Filled n=2
shell
Filled n=3
shell Filled n=4 shell
Filled n=5
shell
Electron Shielding – outermost electrons
are not held as tightly to the nucleus due
to the inner electrons “shielding” them
General Trend in Ionization Energies
Increasing First Ionization Energy
Incre
asin
g F
irst Io
niz
atio
n E
ne
rgy
ATOMIC RADIUS
Atomic radius = ½ the distance from the center to the center of
2 like atoms that are bonded
Atomic Radii
ELECTRONEGATIVITY
Ability of an atom in a compound to attract
electrons
Fluorine has highest electronegativity value
ELECTRON AFFINITY
Electron affinity = energy change when a
neutral atom gains an electron
Cation is always smaller than atom from which it
is formed.
Anion is always larger than atom from which it is
formed.
ION SIZE
Comparison of Atomic Radii with Ionic Radii