Transcript In modern periodic table, elements in the same column have

PSC Chap. 4
The Periodic Table
In modern periodic table,
elements in the same column have
similar properties.
John Newlands - Law of Octaves
– arranged first 16 elements in order of atomic
mass
– found that similar properties were found every
8th element
Dmitri Mendeleev - invented the
modern periodic system - basis of
the modern periodic table
– arranged all known elements in order of atomic
mass
– placed elements w/ similar properties in vertical
columns
A couple of problems w/
Mendeleev's table
• Some elements did not fit into the right
columns when put in order of atomic mass.
If switched, they fit.
– -ex. Te and I, Co and Ni
A couple of problems w/
Mendeleev's table
• In order to put some elements in the right
column, gaps had to be left in his table.
• He predicted elements would be discovered
to fill the gaps
• Also correctly predicted properties of these
undiscovered elements
Henry Mosely, using X-rays,
discovered the atomic number of
elements.
When elements in Mendeleev's
table were placed in order of
atomic number, they fell into the
right columns.
Periodic Law
• - the physical and chemical properties of
elements are a periodic function of their
atomic numbers
Period or Series
• elements that form a horizontal row in the
periodic table
• all elements in the same series have the
same outer energy level
Group or Family
• elements that form a vertical column in the
periodic table
• elements in the same group have similar
electron configurations
• also have similar properties.
Periodic Table can be divided
into 2 regions
• Metals - left side of
table
– good conductors of
electricity and heat
– shiny
– malleable
– groups 1-12 and some
of groups 13-16
• Nonmetals - right side
of table
– poor conductors of
electricity and heat
– dull
– brittle
– some of groups 14 -16
and all of groups 17 &
18
Metalloids
• Semiconductors (semi-metals)
• Have properties of both metals and
nonmetals
• lie on dividing line
• used to make transistors and computer chips
Main-Group Elements
• Also called representative elements
• s and p block elements
• have consistent electron configurations
Group 1
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•
•
•
Alkali Metals
all end in s1
lose the outer e- to form +1 ions
Very reactive metals
React w/ water and oxygen
soft
Group 2
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•
•
•
•
Alkaline Earth Metals
Active metals
end in s2
lose 2 outer e-’s to form +2 ions
not as soft as group 1 metals
Transition Metals
• d block elements
– highest energy e-’s are in the d sublevel
• not as reactive as groups 1 and 2
• have varied properties
Lanthanides and Actinides
• f block elements
– highest energy e-’s are in the f sublevel
• sometimes called rare earth elements or
inner-transition elements
• Lanthanide series fills 4f sublevel
– shiny, reactive, irregular configurations
Lanthanides and Actinides
• Actinide series fills 5f sublevel
– radioactive
Group 16
• Chalcogens
• Contains active nonmetals (top) to
metalloids to less active metals
• end in s2p4
• nonmetals gain 2 e-’s to form -2 ions
Group 17
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•
•
•
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Halogens
Most reactive nonmetals
react with metals to form salts
end in s2p5
gain 1 e- to form -1 ions
Group 18
• Noble Gases
• Mostly unreactive
• end in s2p6
Hydrogen
• In a class by itself
• Behaves unlike other elements because it
has only 1 p+ and 1 e• Most common element in the universe
• Properties of elements are determined
by their electron configurations.
• Elements with similar properties have
similar electron configurations.
Periodic Trends
• Atomic radii
• Reactivity
Atomic radius
• Atomic radius increases as you move down
a group
– Add an energy level as you move down
• Atomic radius decreases as you move
across a period
– Increased nuclear charge pulls e- cloud in
tighter
Reactivity of Metals
• Metals tend to lose e-’s
• As you move down a group, reactivity of
metals increases
– Atoms are bigger and e-’s are held less tightly
• As you move to the left, reactivity of metals
increases
– atoms are bigger to the left
Reactivity of Metals
• The most active metal is in the lower left
corner of the periodic table.
• Fr
Reactivity of Nonmetals
• Nonmetals tend to gain e-’s
• As you move up a group, reactivity of
nonmetals increases
– Atoms are smaller and hold e-’s more tightly
• As you move to the right, reactivity of
nonmetals increases (noble gases not
considered)
– Atoms are smaller
Reactivity of Nonmetals
• The most active nonmetal is in the upper
right corner of the periodic table.
• F