Download The Periodic Table

The Periodic Table
Chapter 6.1
Periodicity
• something that repeats in a specific
manner.
Lists of known elements
• In the 1790s Lavoisier complied a list
of known elements (23)
• Many new elements were discovered
in the 1800s
– electricity allowed compounds to be
broken into elements
– industrial revolution led to chemistry
based industries
– spectrometer allowed elements to be
identified
1860-1870
• In the 1860s chemists agreed on a
method to accurately determine
atomic mass
• By 1870 there were 70 known
elements
– chemists were overwhelmed learning the
properties of so many new chemicals
– think of a Walmart where nothing is
organized. It’s all just thrown wherever
and you have to search through all of it.
John Newlands
• arranged elements
by increasing
atomic mass and
realized properties
were repeated
after every 8th
element. He called
this the law of
octaves (just like
music):
– element 1 and
element 9 behaved
similarly
John Newlands
• harshly criticized for his analogy to
music
• his rows became column in our
periodic table
Dmitri Mendeleev
• showed a
connection between
atomic mass and
properties
• arranged elements
by increasing
atomic mass in
columns and
grouped by physical
and chemical
properties
Dmitri Mendeleev
• predicted the existence and
properties of unknown elements
• He left gaps for these unknown
elements
• some elements were ordered
incorrectly
Henry Mosely
• discovered each
element has a
unique number of
protons
• arranged elements
by increasing
atomic number
(protons)
Henry Mosely
• saw clear periodic pattern of
elements (periodic law)
• brought order to seemingly unrelated
facts
Periodic Law
When elements are arranged
in order of increasing atomic
number, there is a periodic
pattern in their physical and
chemical properties.
Boxes in the Periodic Table
• each box gives:
– element name
– element symbol
– atomic number (=
number of protons)
– atomic mass
(weighted average
mass of all isotopes
of that element)
Periods:
• horizontal rows ( ) on the periodic table
• there are 7 periods
• the periods correspond with the number of
electron shells or energy levels
• As you go from left to right across a period,
the number of protons (atomic number)
increases by 1.
Groups/Families:
The vertical
columns on the
periodic table.
The elements in any group of the periodic
table have similar physical and chemical
properties because they have the same
number of valence electrons!
Question!
How are periods and groups/families on
the periodic table different?
Use this sentence stem:
One way periods and groups/families on
the periodic table are different is …….
Modern Periodic Table
• Group A elements are called
representative elements
• Group B elements are called
transition elements
Classification Groups
• elements can be classified as:
– metals
– nonmetals
– metalloids
• divides along the zigzag line
Metals
• On the left side of the periodic table:
– Exception: Hydrogen IS NOT a metal
•
•
•
•
•
•
High luster (shiny)
solids at room temperature
Good conductors electricity and heat
Ductile (forms wires)
Malleable (bendable/shapable)
all group B elements are metals
Alkali Metals
Alkali Metals
• Soft, shiny metals that can be cut
with a butter knife
• alkaline means base (high pH)
• group 1A elements (except hydrogen)
• very reactive elements
• Reacts violently with water
• never found as elements in nature
(always in a compound)
Alkali Metals
• Alkali Metal Video
Alkaline Earth Metals
Alkaline Earth Metals
• group 2A elements
• reactive, but slightly less reactive
than alkali metals (group 1A)
• found in the earth’s crust
– Emeralds are made of beryllium
Transition Metals
These elements are also
called the rare-earth
elements.
InnerTransition Metals
Transition Elements
• transition metals
– conduct heat and electricity
– high luster when polished
• inner transition metals
– lanthanide series (phosphors that emit
light when struck by electrons. how
television works)
– actinide series (along the bottom)
Nonmetals
• shown in yellow in your textbook
• upper right hand corner of periodic
table
• gases or dull looking brittle solids
• do NOT conduct heat or electricity
well
• Br is the only liquid nonmetal
Halogens
Halogens
• Group 7A elements
• extremely reactive
• halogen comes from a Greek word
meaning giving rise to salt
• combine with other elements to form
salts
Noble Gases
Noble Gases
• Group 8A
• All gases
• Unreactive: inert, stable, don’t form
compounds
• Have complete valence shells
Metalloids
• shown in green boxes in your
textbook
• along the stair step line
• have physical and chemical properties
that are
– metal like
– nonmetal like
• Silicon is used in computer chips
• Germanium is used in solar cells
Periodic Trends
Atomic Radii
• Atomic radius – one half the distance
between the nuclei of two atoms of a
molecule.
Atomic Radii
• Decrease across the periods.
– Caused by the increasing positive charge of the
nucleus
• Increase down the group ( A few exceptions)
– Outer electron is in higher energy levels –
farther from the nucleus.
Group trends
• As we go down a group
H
Li
• Each atom has another
energy level (electron
shell),
• So the atoms get bigger.
Na
K
Rb
Ionic Radii
• Ion: an atom or a bonded group of atoms that has a charge
• Cation – positive ion
– Loss of electron; decrease in radius (smaller)
– Protons pull harder on the electrons to pull them in tight
• Anion – negative ion
-Gain of electron; increase in radius (larger)
-the nucleus is less powerful than the electron cloud so it
expands.
Ionic Radii
• Metals on the left form cations
• Nonmetals on the right form anions
• As you move to the right on the Periodic Table,
the size of an ion decreases.
• As you move down a column, the size of an ion
increases
Question
• What is the difference between
atomic radius and ionic radius?
• Write this Stem in your notes: The
difference between atomic and ionic
radius is ……
• When you are finished writing, put
pencil down and look up.
• When everyone is finished, we will
share.
Ionization Energy
• The energy required to remove an
electron from an atom
• As you move across a period, the
ionization energy increases.
• Down the Groups, the ionization
energy decreases.
– Caused by the increased size of
the atoms. The electrons that
are farther from the nucleus
are easier to remove
Ionization Energy
Another Way to Look at Ionization
Energy
Electronegativity
• The pull a nucleus has on the electrons of a
neighboring atom during a chemical bond.
• Metals lose electrons so they have low
electronegativity's.
• Non-metals gain electrons so they have
high electronegativity's (exception: noble
gases are NOT electronegative)
• Generally, electronegativity increases from
left to right and decreases from top to
bottom.
Electronegativity
Summation of Periodic Trends