Transcript The Periodic Table

The Periodic Table
Chapter 6
www.webelements.com
Why is the Periodic Table
important to me?
 The periodic table is the
most useful tool to a
chemist.
 You get to use it on
every test.
 It organizes lots of
information about all the
known elements.
Pre-Periodic Table Chemistry …
 …was a mess!!!
 No organization of
elements.
 Imagine going to a
grocery store with no
organization!!
 Difficult to find
information.
 Chemistry didn’t make
sense.
ORGANIZING THE ELEMENTS
 J. W. Dobereiner (a German) in 1829 used
the chemical properties of the elements to
sort them in groups of threes (triads).
 Dimitri Mendeleev (a Russian) in 1869 used
increasing atomic mass to order the
elements.
 (Remember proton was not discovered until
1886—nucleus in 1911.)
Dmitri Mendeleev: Father of the
Table
HOW HIS WORKED…
 Put elements in rows by
increasing atomic mass.
 Put elements in
columns by the way
they reacted.
SOME PROBLEMS…
 He left blank spaces for
what he said were
undiscovered elements.
(Turned out he was
right!)
 He broke the pattern of
increasing atomic mass
to keep similar reacting
elements together.
The Current Periodic Table
 Now the elements are put in rows by
ATOMIC
NUMBER!!
increasing
 The horizontal rows are called periods and
are labeled from 1 to 7.
 The vertical columns are called groups are
labeled from 1 to 18 (and 1A-8A).
THE PERIODIC LAW
When elements are arranged in
order of increasing atomic
number, there is a periodic
repetition of their physical and
chemical properties.
Three classes of elements are:
 Metals






Good conductors of heat
Good conductors of electricity
Shiny
All are solids at room temperature except
mercury (Hg)
Ductile—can be drawn into wire
Malleable—can be hammered into a sheet
Three Classes of elements:
 Nonmetals (properties vary more than
metals)





Poor conductors (except carbon)
Brittle (shatter when hit)
Most are gases at room temperature
Sulfur and phosphorus are solids
Bromine is a liquid
Three Classes of elements
 Metalloids


They behave as metals and nonmetals
depending on conditions
If boron is added to silicon, then silicon will
conduct electricity = semiconductor
Squares in the periodic table
Groups = vertical columns
 Elements in
the same
group have
similar
chemical and
physical
properties!!
 (Mendeleev did that on
purpose.)
Why??
• They have the same
number of valence
(outer energy level)
electrons.
• They will form the same
kinds of ions (charged
atoms).
Reactivity GROUPS
 REACTIVITY INCREASES AS YOU GO
DOWN A GROUP OF METALS
 REACTIVITY DECREASES AS YOU GO
DOWN A GROUP OF NONMETALS
Alkali Metals –s1 (2s1 – 7s1)
 1st column on the
periodic table (Group 1
or Group 1A) not
including hydrogen.
 Very reactive metals,
always combined with
something else in
nature (like in salt).
 Soft enough to cut with
a butter knife
Alkali metals
Cesium in water
Electron Configuration of Group
1A
Hydrogen
 Hydrogen belongs to a
family of its own.
 Hydrogen is a
diatomic—always H2,
reactive gas.
 Hydrogen was involved
in the explosion of the
Hindenberg.
 Hydrogen is promising
as an alternative fuel
source for automobiles
Alkaline Earth Metals –s2 (2 s2 - 3 s2 )
 Second column on the
periodic table. (Group 2
or 2A)
 Reactive metals that
are always combined
with nonmetals in
nature.
 Several of these
elements are important
mineral nutrients (such
as Mg and Ca
Alkaline Earth Metals
Transition Metals (d-block d1- d10)
 Elements in groups 3-12
 Less reactive harder metals
 Includes metals used in
jewelry and construction.
 Metals used as
“uncombined” element
metal.
 The transition elements often
act as catalysts in reactions
and are often colorful in
compounds.
Transition metals
 The Group B elements
Boron Family p1 (2 p1 - 6 p1 )
Elements in group 13 (3A)
Boron is most commonly found as
borax and boric acid, which are
used in cleaning compounds.
Aluminum is the third most common
element in the earth's crust. It is
used as a coating agent, to prevent
oxidation. It is an excellent
conductor of electricity and heat and
can be found in many cooking
utensils. Gallium is important today
in the production of gallium arsenide
LEDs and laser diodes. Indium is a
very soft metal that can actually be
wiped onto other metals as an
anticorrosion agent. It also has the
peculiar quality of squealing when
bent. Finally, thallium is quite toxic
and is sometimes used in rat
poisons. It has also been used in
glass to make special infrared
filters.
Boron Family
Carbon Family
p2 (2 p2 -6 p2)
 Elements in group 14
(4A)
 Contains elements
important to life and
computers.
 Carbon is the basis for
an entire branch of
chemistry.
 Silicon and Germanium
are important
semiconductors.
More about the carbon family
 The element carbon is the basis of life. It is found in
all living material. Silicon is a semiconductor used
commonly in computer chips and solar cells. It is also
the second most abundant element in the earth's
crust. Silicon dioxide, SiO2, is the major component
of glass. Germanium has important semiconductor
properties and is used in the computer industry. It is
one of the few elements that expand when frozen.
Lead has long been used for plumbing and is also
used to block radiation. Tin was once used to make
cans because it is relatively stable -- unreactive.
Aluminum has replaced the more expensive tin
today.
Electron configuration of Group
4A
Carbon Family
Nitrogen Family
p3 (2 p3 - 6 p3)
 Elements in group 15 (5A)
 Nitrogen makes up over ¾
of the atmosphere.
 Nitrogen and phosphorus
are both important in living
things.
 Most of the world’s nitrogen
is not available to living
things.
 The red stuff on the tip of
matches is phosphorus.
 http://www.carondelet.p
vt.k12.ca.us/Family/Sci
ence/Nitrogen/thefamily
.html
More about the nitrogen family
 Nitrogen is used in saltpeter for fertilizer and
explosives. It is also useful to create an oxygen-free
atmosphere to prevent oxidation or combustion. A
common use for liquid nitrogen today is the rapid
freezing of food products. We also use liquid nitrogen
in medical/surgical applications such as cryotherapy
and cryosurgery. Phosphorus is used in compounds
such as phosphoric acid, to make synthetic fertilizers,
and in detergents. Arsenic and antimony are most
commonly found in alloys used for the production of
batteries and special types of solder. Bismuth is
commonly used for alloys of metals and as a
component of cosmetics or medicine used to treat
upset stomach (Pepto-Bismol) and eczema.
Oxygen Family or Chalcogens p4
2 p4 - 6 p4)
 Elements in group 16
(6A)
 Oxygen is necessary for
respiration.
 Many things that stink,
contain sulfur (rotten
eggs, garlic,
skunks,etc.)
The chalcogens (Oxygen family)
More about the oxygen family
 Oxygen and sulfur are common elements. In fact, oxygen is the
most common element (by mass) in the earth's crust. Because
oxygen is second in electronegativity only to fluorine, it reacts
with almost everything to form compounds here on earth.
Selenium has some semimetal characteristics, such as an
increase in electrical conductivity when a light is shined on it.
Tellurium is a true semimetal, existing in compound with both
positive and negative charges. Polonium is an extremely rare
radioactive element discovered by Marie Curie and named for
her native Poland. This means that the oxygen family is split
between nonmetals and semimetals.
Halogens p5 (2 p5 - 6 p5)
 Elements in group 17
(7A)
 Very reactive, volatile,
diatomic, nonmetals
 Always found combined
with other element in
nature .
 Used as disinfectants
and to strengthen teeth.
The halogens
More about the halogens:
 All of the elements of the halogen family are found in
common use in everyday life. Fluorine is used in
compounds to strengthen the enamel of your teeth
against decay. It is also used in acid form to etch
glass. Chlorine is used in our drinking water and in
swimming pools to inhibit bacterial growth. It is also
used in the form of chlorine dioxide to bleach wood
pulp in the manufacture of very white paper. We also
use chlorine in everyday laundry bleach. Chlorine
compounds are used in insecticides, fireworks, and
matches.
The representative elements (1A-7A)
 Display a wide range of physical and
chemical properties.
 They are metals, nonmetals and metalloids.
 At room temperature: most are solids, some
are gases and one is a liquid.
 The group number = number of electrons
in outer energy level
 The elements in the 1A-7a groups
1A
are called the representative
2A elements
3A 4A 5A 6A 7A
8A
0
The Noble Gases

The noble gases are used in
industry in arc welding, to dilute the
oxygen in deep-sea divers' gas
tanks, and to fill light bulbs. Argon is
used in arc welding and in common
light bulbs, as it does not react with
the metal at high temperatures.
Helium is used for diluting the pure
oxygen in deep-sea diving tanks
because the helium has a low
solubility in human blood. Helium is
also used to inflate the tires of large
aircraft, weather balloons, and
blimps because it is nonflammable.
Neon is used in sign tubing because
it glows bright red when electricity is
passed through it. Krypton and
xenon are used in photographic
flash units and in lighthouses, as
running an electric current through
either element generates a very
bright light.
The Noble Gases p6 (2 p6-6 p6)
except for He =1s2
 Elements in group 18




(8A)
VERY unreactive,
monatomic gases
Used in lighted “neon”
signs
Used in blimps to fix the
Hindenberg problem.
Have a full valence
shell.
The Noble Gases
More Noble Gases
 Since all noble gases
are colorless, odorless
gases at room
temperature, here are
some pictures of how
you might find them in
use.
 Xenon in headlights
 Radon leaking into
homes.
Electron Configurations in Groups
 Noble gases:
Transition metals the “d” block
inner
transition
metals
the
“f”
block
 Group 3-12 (B)
Periodic Trends
Section 6.3
Reasons for the trends:
Pull of the nucleus on electrons vs.
shielding effect of electrons in new energy
levels
Pull of nucleus vs. electrons
Increases across a
period
Decreases down a
group
Pull of the nucleus
 In a neutral atom, the pull between
the electrons and protons is equal.
 In an ion the pull is unequal.
Shielding effect
 As the atomic number increases
down a group, the energy level
increase (Li, level 2, Cesium, level
6) so…
 The increase in energy levels
shields electrons from the pull of
the nucleus.
Atomic Radius decreases across a
period
Pull of the nucleus: There are
more electrons and more
protons within the same energy
level=more pull
Sheilding effect is not a factor
Atomic Radius increases down a group
The shielding effect of more
energy levels is greater than the
increased pull of the nucleus on
electrons (between more
electrons and protons.)
Ionic radius
 Cations are always smaller than anions
 Cations are smaller than their atom
 Anions are larger than their atom
Ionic radius decreases across a period
 Size of cations decreases
 Size of anions decreases
 More pull by the nucleus because there is no
increase in shielding effect
Ionic radius generally increases down
a group
Because there is an increase
in number of energy levels
(shielding effect)
Ionization energy increases across a
period
There is a stronger pull
between electrons and
protons in the nucleus.
The shielding effect is
constant and therefore not a
factor.
Ionization energy decreases down a
group
 Pull of the nucleus is minor
 SHIELDING EFFECT is the major
reason that atoms can release an
electron easier
Electronegativity
the ability of an atom of
an element to attract
electrons when an
atom is in a compound
Electronegativity increases across a
period
Metals have low values
because they have few
electrons in outer energy
level
 and non-metals have
high values because they
need only a few electrons.
Electronegativity decreases down a
group
Cs (cesium)is lowest on
table and F (fluorine) is
highest
Electronegativity increases across a
period
 Pull of nucleus on electrons from other atoms
is strong
 Shielding effect does is not a factor
Electronegativity decreases down a
group
 Shielding effect is a factor on an atoms ability
to pull in electrons from another atom
 Increased pull from nucleus is not a major
factor.
A3-D view of electronegativity
Credits:
 http://www.hcc.mnscu.edu/chem/V.10/alkaline_earth_metals.jpg
 http://www.hcc.mnscu.edu/chem/V.10/halogens.jpg
 http://images.google.com/imgres?imgurl=http://www.learner.org/
interactives/periodic/images/boron.gif&imgrefurl=http://www.lear
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 http://www.dkimages.com/discover/previews/
796/939300.JPG