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Why is the Periodic
Table Important?
1s22s22p63s23p64s23d6
26
Fe
IRON
55.85
Atomic Number
– # of protons
– # of electrons
Element Symbol
Atomic Mass
– Weighted average
of isotopes
– Molar mass in g/mol
These Three Elements are Chemically Similar
6.1
What do they have in common?
• They appear very different.
• Chlorine is a toxic,
poisonous gas that was
used during the trench
warfare phase of World War
I (mustard gas!)
• Bromine is a dark red liquid.
• Iodine is a dark solid with an
almost metallic luster.
Handouts
• PT Familiarity
• Periodic Table Coloring
Metals, Non-Metals and Metalloids
Metals Conduct Heat well!
What happens?
Metals Conduct Electricity Well.
What happens?
14
Properties of Metals
• Good Conductors of
– Heat
– Electricity
• Malleable
– Can be pounded into thin
sheets (aluminum foil)
• Ductile
– Can be stretched into thin
wire (copper wire)
• High Melting Points
Properties of Non-Metals
• Poor conductors of heat
• Poor conductors of
electricity
• Mostly gases at room
temperature
Explain this picture!
Noble Gases
• Column 18 or 8a
• Inert and non-reactive gases.
• Full valence electron shell.
• They tend to not lose or gain
electrons.
6.2
Electron Configurations in Groups
The Noble Gases
The noble gases are the elements in Group 8A of the
periodic table. The electron configurations for the first
four noble gases in Group 8A are listed below.
Two Odd Elements
Bromine (liquid non-metal)
Mercury (liquid metal)
A coin floating on Mercury. Why?
Halogens
• Column 17 or 7a
• Highly reactive.
• Halogens are “salts”.
• These elements combine with
Column 1A and 2A elements to
create salts.
• Will gain a single electron.
http://www.youtube.com/watch?v=U0CGsw6h60k
Move over Lady Gaga
Rihanna is here….
Alkali Metals
• Shiny, soft, highly
Reactive Metals!
• Will lose their single
valence electron.
• Catch fire and may
explode in water.
6.2
Electron Configurations in Groups
ALKALI Metals:
In atoms of the Group 1A elements below, there is only
one electron in the highest occupied energy level.
Alkaline Earth Metals
• Column 2A
• Shiny, silvery-white,
somewhat reactive
Metals
• Give off beautiful colors
• Combine with the
halogens to form
metallic salts.
Columns 1A and 2A elements make
pretty colors….
Metalloids
• Elements that have the
properties of both
metals and non-metals.
• Semi-Conductors:
6.1
• If a small amount of boron is mixed with silicon, the
mixture is a good conductor of electric current. Silicon
can be cut into wafers, and used to make computer
chips.
Transition Metals
• Groups 3-12 on
the periodic
table.
• Defined by an
incomplete d
sub-shell.
Other Metals
• Valence electrons reside
in the p sub-shells.
• Differ from transition
metals in terms of
oxidation number.
Periodicity and Periodic Law
6.1
An Early Version of Mendeleev’s Periodic Table
Arranged in Order of Increasing Atomic Mass
6.1
The Periodic Law
Periodic Law: When elements are arranged in order of
increasing atomic number, there is a periodic repetition
of their physical and chemical properties.
•Atomic Size: Decreases
•1st ionization Energy: Decreases
•Nuclear Charge: Increases
•Electron Shielding: Remains Constant
•Metals: Reactivity Decreases
•Non-Metals: Reactivity Increases
•Electronegativity Increases
•Cation size: decreases, Anion size: Increases
1
•Atomic Size Increases
•1st ionization Energy Increases
•Nuclear Charge Increases
•Electron Shielding: Increases
•Metals: Reactivity Increases
•Non-Metals: Reactivity Decreases
•Electronegativity: Decreases
•Ionic Size: Generally Increases
VALENCE ELECTRONS
8
34 56 7
2
•Atomic Size Decreases
•1st ionization Energy Decreases
•Nuclear Charge Increases
•Electron Shielding Remains Constant
•Metals: Reactivity Decreases
•Non-Metals: Reactivity Increases
•Electronegativity Increases
•Cation size decreases, Anion size
Increases
1
•Atomic Size Increases
•1st ionization Energy Increases
•Nuclear Charge Increases
•Electron Shielding Increases
•Metals: Reactivity Increases
•Non-Metals: Reactivity Decreases
•Electronegativity Decreases
•Ionic Size Generally Increases
8
2
VALENCE ELECTRONS
3 4 5
6 7
Coulomb’s Law
EFFECTIVE NUCLEAR CHARGE
The nucleus itself has a +9 charge and
anything in its vicinity will feel that
charge. The two electrons in the first
energy level as they look at the
nucleus feel a +9 charge because that
is the charge on the nucleus. But the
electrons that are in the valence
energy level would be shielded from
the nucleus by the 2 shielding
electrons. The +9 nuclear charge is
shielded by 2 electrons to give an
effective nuclear charge of +7 that is
felt by the valence electrons. If you get
out beyond the valence electrons, then
the effective charge is 0 simply
because the +9 charge of the nucleus
is surrounded by 9 electrons.
• Fluorine Atom
Nuclear Charge
F
Shielding
Electrons
Valence
Electrons
1s2
2s22p5
+9
2
Effective Nuclear Charge
+7
What charge is felt by the electrons in the first level of a
neon atom?
What charge is felt by the electrons in the second level
(valence level) of a neon atom?
What charge is felt by the electrons in the first level of a
sodium atom?
What charge is felt by the electrons in the second level
of a sodium atom?
What charge is felt by the electrons in the third (valence)
level of a sodium atom?
What charge is felt by the electrons in the first
level of a neon atom? 10
What charge is felt by the electrons in the
second (valence) level of a neon atom? 8
What charge is felt by the electrons in the first
level of a sodium atom? 11
What charge is felt by the electrons in the
second level of a sodium atom? 9
What charge is felt by the electrons in the third
(valence) level of a sodium atom? 1
Trends in Nuclear Charge and
Electron Affinity:
Blank Periodic Table
AufbauBoxes
Put Students into Groups and have them
write electron configuration for the first 3
elements each Group in the PT
Students write them on the board and
sharre the data and identify the trends….
6.3
Trends in Atomic Size
Trends in Atomic Size
What are the trends among the elements for
atomic size?
6.3
Trends in Atomic Size
The atomic radius is one half of the distance between
the nuclei of two atoms of the same element when the
atoms are joined.
6.3
Trends in Atomic Size
Group and Periodic Trends in Atomic Size
– In general, atomic size increases from top to bottom within a
group and decreases from left to right across a period.
6.3
Trends in Atomic Size
6.3
Trends in Atomic Size
6.3
Ions
•Positive and negative ions form when electrons are
transferred between atoms.
6.3
Ions
• Some compounds are composed of particles called
ions.
An ion is an atom or group of atoms that has a positive or
negative charge.
A cation is an ion with a positive charge.
An anion is an ion with a negative charge.
Ionization Energy
• The energy required to remove an electron from an
atom is called ionization energy.
The energy required to remove the first electron from an atom is
called the first ionization energy.
The energy required to remove an electron from an ion with a
1+ charge is called the second ionization energy.
6.3
Trends in Ionization Energy
Group and Periodic Trends in Ionization Energy
• First ionization energy tends to decrease from top to
bottom within a group and increase from left to right
across a period.
6.3
Trends in Ionization Energy
6.3
Trends in Ionization Energy
6.3
Trends in Ionization Energy
6.3
Trends in Ionic Size
Trends in Ionic Size
• During reactions between metals and nonmetals, metal
atoms tend to lose electrons, and nonmetal atoms tend
to gain electrons. The transfer has a predictable effect
on the size of the ions that form.
6.3
Trends in Ionic Size
• Cations are always smaller than the atoms from
which they form. Anions are always larger than
the atoms from which they form.
6.3
Trends in Ionic Size
• Relative Sizes of Some Atoms and Ions
Size generally increases
6.3
Trends in Ionic Size
6.3
Trends in Electronegativity
Trends in Electronegativity
• Electronegativity is the ability of an atom of an
element to attract electrons when the atom is in a
compound.
In general, electronegativity values decrease from top to bottom
within a group. For representative elements, the values tend
to increase from left to right across a period.
6.3
Trends in Electronegativity
Representative Elements in Groups 1A through 7A