Transcript Document 7182245

The Periodic Table of the
Elements
Classification of Elements
 Pure substances are either
compounds or elements.
 Compounds can be broken down
into simpler substances, but
elements cannot because they
are made of only one kind of
atom.
 In the last three centuries, new
technologies led scientists to try
to identify all of the existing
elements and group them into
similar categories.
 Currently, scientists have
identified 112 different elements.
92 of them occur naturally, and
20 are man-made. Scientists
build super-heavy atoms to test
the limits of atomic structure.
 During the eighteenth and
nineteenth centuries, scientists
noticed that some elements
behaved like other elements.
 By comparing the behaviors of
elements, scientists identified
several groups of elements.
 Other scientists of that time were
able to determine the relative
atomic masses of different
elements.
 These discoveries led to the
development of the Periodic
Table of the Elements, which is
an important tool of chemists.
The First Periodic Table
 Dmitri Mendeleev is known as the
father of the Periodic Table.
 He was born in Russia in 1834.
As were many other scientists of
the time, Mendeleev was
interested in discovering if a
pattern existed relating the
known elements.
 Mendeleev discovered that the
physical and chemical properties
of the elements occurred in a
regular repeating pattern—the
Periodic Law.
 He published his Periodic Table
of the Elements in 1869, the first
table that successfully
summarized the relationships
between the elements.
 In this table, he arranged the
known elements in ascending
order according to their relative
atomic masses, beginning with
Hydrogen.
 Mendeleev also arranged the
elements in columns according to
their physical and chemical
properties.
 Mendeleev’s table pointed out
some errors in accepted atomic
weights, and also predicted the
existence and properties of
elements not yet discovered.
 Mendeleev’s table did not include
any of the noble gases, because
none of them had been
discovered.
Revision of Mendeleev’s Table
 In Mendeleev’s table, there were
some elements that appeared to
be in the wrong group if arranged
strictly by increasing atomic
weight. As more elements were
discovered after Mendeleev’s
death, a few more “misplaced”
elements appeared.
 Some elements, such as Ni, were
placed in the wrong groups
because of multiple valence
numbers or errors in the
calculation of their atomic
weights.
 In 1914, Henry Moseley
discovered the significance of
atomic number, the number of
protons in the nucleus of an atom.
 When the Periodic Table was
revised, arranging the elements
by ascending atomic number, the
inconsistencies and errors in the
table vanished.
 The Modern Periodic Table of the
Elements has been modified so
that the elements are now
arranged by atomic number,
rather than atomic weight.
 The Table has seven horizontal
rows, called periods, and a
number of vertical columns
called groups or families.
 Elements in the same period have
the same number of occupied
energy levels.
 Elements in the same group or
family have similar properties.
Metals, Nonmetals, and Metalloids
 There are 92 naturally occurring
and 13 man-made elements listed
on the Periodic Table, with space
left for future creations.
 These elements can be divided
into three basic types, according
to their chemical and physical
properties: metals, nonmetals, and
metalloids.
 Most of the elements are metals.
Characteristics of metals include:
high luster, high malleability, high
ductility, good conductivity of heat
and electricity, and have high
melting and boiling points. Metals
tend to lose electrons in chemical
bonding, forming positive ions.
 Metals are found on the left side of
the Periodic Table.
 Nonmetals are found on the right
side of the Periodic Table.
 Nonmetals are generally dull,
brittle, non-malleable, nonductile, with low melting and
boiling points. Many are gases at
room temperature. They are nonconductors of heat and
electricity.
 Nonmetals form negative ions
because they tend to gain
electrons during chemical
bonding.
 Metalloids have some of the
properties of metals and some
properties of nonmetals. They
are found between metals and
nonmetals in the Periodic Table,
next to the zigzag line.
The Alkali Metals – Group IA
 The Alkali Metals are found in the first group of the Periodic
Table. They are a group of elements that are so reactive
that they are always found combined with other elements in
nature.
 The reason that these elements are so reactive is that they
only have one electron in their outer shell, which they lose
when bonding with other elements, to get a full outer shell
of electrons. The alkali metals form +1 ions.
 Alkali Metals are malleable and ductile, good conductors of
heat and electricity, but are very soft.
 The alkali metals include Lithium, Sodium, Potassium,
Rubidium, Cesium, and Francium.
 Alkali metals can explode when in contact with water.
 Cesium and Francium are the most reactive in this group.
 Francium is the most reactive of all metals.
 Although Hydrogen is a nonmetal, it is often listed with this
group because it has one electron in its only energy level.
Hydrogen is highly reactive but only forms covalent bonds.
H
Li
Na
K
Rb
Cs
Fr
The Alkaline Earth Metals
 The Alkaline Earth Elements are found
in the second group of the Periodic
Table.
 Even though they are not as reactive
as the alkali metals, the alkaline earth
metals are highly reactive, and are not
found in the elemental state in nature.
 Each of the alkaline earth metals has
two electrons in its outer energy level.
Alkaline earth metals lose their two
valence electrons and form +2 ions
when bonding.
 The alkaline earth elements include
Beryllium, Magnesium, Calcium,
Strontium, Barium, and Radium.
Be
Mg
Ca
Sr
Ba
Ra
The Boron Family
 The Boron Family is the third group on the
Periodic Table. The members of this family
have three electrons in their outer shell.
Although Boron is never found uncombined in
nature, some of the other members of this family
sometimes are.
 Members of the Boron Family tend to lose three
electrons and form +3 ions.
 Boron is a metalloid, and all other group
members are metals.
 Aluminum is found in this group. It is the most
abundant metal on Earth. It is generally found in
nature as aluminum oxide.
 Other elements found in this family are Gallium,
Indium, and Thallium.
 Although Boron is a metalloid, all other
elements in this family are metals.
B
Al
Ga
In
Tl
The Carbon Family
 The Carbon family is the fourth group, and contains one
nonmetal, two metalloids, and two metals. All members of
the carbon family have four electrons in their outer energy
level. Members of this family include Carbon, Silicon,
Germanium, Tin, and Lead. Members of this family tend to
form covalent bonds.
 Carbon is the sixth most abundant element in the universe,
but not as common on Earth.
 Carbon exists in several bonding forms such as graphite
and diamonds. C-14 is used in radiological dating of some
fossils.
 It can form four covalent bonds with other elements and
even other carbon atoms, resulting in an almost infinite
number of carbon-containing compounds. Life on earth
would be impossible without carbon.
 Silicon is also found in the Carbon Family. It is the second
most abundant element in the Earth’s crust, and is used in
solar-electric cells and semi-conductors. Germanium is
also used in electronic devices. Tin and lead have a
number of uses.
C
Si
Ge
Sn
Pb
The Nitrogen Family
 The Nitrogen Family is the fifth group and contains two
nonmetals, two metalloids, and only one metal. They all have
five electrons in their outer energy level. They tend to gain
three electrons when forming ionic bonds, and form -3 ions.
 Nitrogen makes up about 4/5 of the Earth’s atmosphere, and
is a colorless, odorless gas at room temperature. It is a
nonmetal. Nitrogen forms many compounds with oxygen,
such as NO2 and N2O.
 Phosphorus occurs naturally in solid form as red phosphorus
or white phosphorus. It is highly reactive and will burst into
flame in the presence of air. It is stored under water.
 Arsenic is a metalloid, and is used in the semiconductor
industry and in manufacturing. It is highly poisonous and is
used in weed killer and rat poison.
 Antimony is a hard brittle metalloid used in electronics. It is,
like arsenic, highly poisonous.
 Bismuth is the heaviest naturally occurring element that is not
radioactive. It has a variety of uses from Pepto-Bismol to
paint pigments, to electrical solder and the heads of fire
sprinkler systems.
N
P
As
Sb
Bi
The Oxygen Family
 Members of the Oxygen Family all have six electrons in their
outermost energy level. The Oxygen Family is the sixth
group on the Periodic Table and contains three nonmetals
and two metalloids. There are no metals in the Oxygen
Family.
 Members of the Oxygen Family tend to gain two electrons
and form -2 ions, when bonding ionically.
 Oxygen is the most common element in the Earth’s crust and
makes up 1/5 of the Earth’s atmosphere. It is a colorless,
odorless gas at room temperature. All elements except the
noble gases can form compounds with oxygen.
 Sulfur is a yellow solid at room temperature. Sulfur is in
sulfuric acid and also in acid rain. It is in the gas H2S, which
smells like rotten eggs.
 Selenium is a semiconductor that is sensitive to light, so it is
often used in light sensors.
 Tellurium is a brittle metalloid used in blasting caps.
 Polonium is radioactive and was discovered by Marie Curie.
It has few commercial uses.
O
S
Se
Te
Po
The Halogens
 All members of the Halogen Group have seven electrons in their
outer energy level. They are the seventh group on the Periodic
Table. This group contains four nonmetals and one metalloid.
There are no metals among the halogens.
 Because they only need one electron to complete their outer
energy level, they are the most reactive of the nonmetals. They
gain one electron and form -1 ions when bonding ionically.
 Fluorine is the most reactive nonmetal and is never found alone
in nature. It is a poisonous greenish-yellow gas at room
temperature. Fluorine compounds are added to many water
systems because they prevent tooth decay. Teflon is a
fluorocarbon compound.
 Chlorine is not as reactive as fluorine, but is also a reactive
poisonous greenish-yellow gas. One of its most common
compounds is NaCl, table salt.
 Bromine is a reddish-brown liquid at room temperature. It is
often used to disinfect hot tubs.
 Iodine is a solid at room temperature that turns to a purple gas
when heated. It is needed in your diet to keep your thyroid
gland functioning properly.
 Astatine is a radioactive metalloid, but not much is known about
its properties.
F
Cl
Br
I
At
The Noble Gases
 The noble gases are the eighth group on the Periodic Table,
and all of the members of this group are unreactive because
their outer electron shell is already full.
 Helium is the second lightest and second most abundant gas
in the universe, but is relatively rare on Earth. Helium has
two electrons in its only energy level. No compounds of
Helium are known. It is used in balloons and blimps.
 Neon is the best known of the noble gases because of its use
in decorative lighting fixtures. It forms no compounds.
 Argon is used to fill incandescent light bulbs to keep the
filament from burning up. It is also used in welding.
 Krypton is not a green solid that hurts Superman. It is an
unreactive gas used in bright strobe lights and airport
runway lights.
 Xenon is a gas that is also used in strobe lights. It can be
forced to react with fluorine, but is ordinarily unreactive.
 Radon is a glowing yellow radioactive noble gas that is
considered to be a health hazard if breathed in large
amounts. It is used in cancer treatments.
He
Ne
Ar
Kr
Xe
Rn
The Transition Metals
 The Transition Metals are the elements found on the Periodic Table between
the Alkaline Earth Metals and the Boron Family.
 While the Transition Metals all have no more than 2 electrons in their outer
energy level, their next energy level is incompletely filled.
 The properties of the Transition Metals depend on the electron configuration
of the outer two energy levels.
 Transition elements form alloys easily. A copper-tin alloy is for mirrors and
copper-zinc makes brass. Except for copper, the transition metals are all
shiny and white, with high melting points and high densities.
 Many of the most commonly known metals, such as gold, silver, mercury,
iron, copper and nickel are in this group.
Sc
Ti
V
Cr
Mn
Fe
Co
Ni
Cu
Zn
Y
Zr
Nb
Mo
Tc
Ru
Rb
Pd
Ag
Cd
La
Hf
Ta
W
Re
Os
Ir
Pt
Au
Hg
Db
Sg
Bh
Hs
Mt
Uun
Uuu
Uub
Ac
Rf
The Rare Earth Elements
 There are 30 Rare Earth Elements. They are all metals, and they are
divided into two sets: The Lanthanide Series begins with element # 57,
Lanthanum and ends with element # 71 Lutetium. The Actinide Series
begins with element # 89 Actinium and ends with element # 103
Lawrencium.
 One element of the Lanthanide Series and most of the elements of the
Actinide series are man-made. Many are radioactive.
 All of the Rare Earth elements are found in Group 3 of the Periodic Table
in the sixth and seventh periods.
La Ce Pr
Nd Pm Sm Eu
Gd Tb
Dy Ho Er Tm Yb Lu
Lanthanide Series
Ac Th Pa
Actinide Series
U
Np Pu Am Cm Bk Cf
Es Fm Md No Lr
A Representative Block on the
Periodic Table
 Each block on the Periodic Table
contains valuable information about
the element listed.
 The name of the element is often
(but not always) listed.
 The element’s chemical symbol is
always listed. This is either one or
two letters. The first is always
capitalized and the second (if there
is one) is never capitalized.
 The Atomic Number tells how many
protons are in the nucleus of an
atom of that element.
 The Atomic Mass tells the average
mass of one atom of that element in
atomic mass units. It can be
rounded off to determine the
element’s mass number.
Atomic Number
8
Chemical
Symbol
Oxygen
16.000
Name of
Element
O
Atomic Mass
Periods, Families, and Electron Configuration
 There are seven periods on the modern Periodic Table.
 If an element appears in the third period (like Magnesium), this
means that in its lowest energy state, the atom’s electrons are in
the first three periods.
 Being located in the third period also means that the atom’s first
two energy levels are full.
 The first energy level can hold 2 electrons. The second energy
level can hold eight electrons.
 Magnesium appears in the Alkaline Earth Family, in the IIA column
of the Table. All elements in the IIA column have 2 electrons in
their outermost energy level.
 Elements in the IA column have 1 electron in their outside energy
level, elements in the VA column have 5 electrons in their outside
energy level, and so forth.
 Elements in Column VIIIA are inert. Their outside energy levels
are full, so they have no need to react to form compounds with
other elements.