Transcript The Periodic Table of Elements

The Periodic Table
of Elements
Early Versions
1830: 55 elements had been
discovered
 1860’s: Dimitri Mendeleev
discovered a system that applied
to all elements

Mendeleev
•Father of the
periodic table
•Noticed patterns
when the
elements were
arranged by
increasing
atomic mass
Mendeleev
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Noted properties of elements
Melting point
 Density
 Color
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Studied atomic mass and chemical
bonds
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Compared mass to hydrogen
Mendeleev
Noted that arranging elements
according to atomic mass did not
always produce similar groups
 Moved element cards into groups
where they fit best
 Predicted other elements and their
properties
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Mendeleev
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1869: Published
the 1st periodic
table
The Modern Periodic Table
New elements were added as
they were discovered
 Early 1900’s: scientists learned
about the atomic number
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Reading the Periodic
Table
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Contains
over 100
squares:
one for each
element
Isotopes
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Atoms of a certain element ALWAYS have
the same # of protons….DO NOT always
have the same mass
 May have different number of neutrons
 Isotope
 Atoms of the same element that have
a different number of neutrons
Isotopes
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Examples:
 Chlorine-35
 Chlorine-37
 Carbon-14
Reading the Periodic
Table
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An element’s properties can
be predicted from its location
on the periodic table.
groups/families
 periods
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Groups/Families
Elements in columns
 18 columns
 Elements in each group have similar
characteristics.
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Example: Group 1 are metals that all
react violently with water; Group 17
reacts violently with elements from
Group 1; Group 18 rarely reacts at all
Groups/Families
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EXAMPLES OF FAMILIES
- Alkali Metals
- Alkaline Earth Metals
- Transition Metals
- Halogen Gases
- Inert Gases (Noble Gases)
Periods
Horizontal rows
 Series of different elements from
different groups
 Have very different properties
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Why it Works!
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It’s based on the
structure of atoms,
especially the valence
electrons!
Metals
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Most elements are metals.
Found to the left of the zig-zag line.
Elements are classified as metals based
on physical properties.
Hardness
 Shininess (luster)
 Malleability
 Ductility
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Physical Properties
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Have luster (shiny)
Good conductors of heat & electricity
(transmit easily)
High density
Very high melting point
Ductile (drawn into thin wires)
Malleable (hammered into thin sheets)
Most are solid at room temperature.
Chemical Properties
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Wide range of chemical properties
Some are very reactive and combine
quickly. (sodium)
Some are unreactive. (gold)
Other metals fall somewhere in between
Corrosion: the process of reaction and
wearing away of metals
Alloys
A mixture of metals
 Combine the best properties of 2 or
more metals into a single substance
 Ex: copper + tin = bronze
 Ex: copper + zinc = brass
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Group 1: Alkali Metals
From Lithium to Francium
 MOST reactive of ALL metals
 NEVER found uncombined in nature;
exist as compounds
 Very soft & shiny
 Have 1 valence electron (lose easily)
 2 MOST IMPORTANT: sodium &
potassium (essential for life)
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Group 2: Alkaline Earth
Metals
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Not as reactive as group 1, but still
more reactive than most metals
NEVER found uncombined in nature
Have 2 valence electrons (lose easily)
2 MOST COMMON: magnesium &
calcium
Magnesium: flash bulbs, alloys for airplanes,
ladders
 Calcium: teeth & bones, muscles
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Groups 3-12: Transition
Metals
Form a bridge between very reactive
metals on the left and less reactive
metals on the right
 So similar to one another that
differences between nearby columns
are difficult to detect
 Include the most familiar metals:
iron, copper, nickel, silver & gold
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Groups 3-12: Transition
Metals
Most are hard and shiny
 All are good conductors of electricity.
 Fairly stable, reacting slowly or not at
all with water and air
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Groups 13-16: Metals in
Mixed Groups
Metals to the right of the transition
metals are not nearly as reactive as
those on the left.
 Most familiar: aluminum, tin, lead
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Lanthanides and
Actinides
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Lanthanides: top row at the bottom of the
periodic table
Actinides: bottom row at the bottom of the
periodic table
Called rare earth elements
Fall between alkaline earth metals and
transition metals
Placed at the bottom for convenience
Lanthanides
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Soft, malleable, shiny metals
High conductivity
Used in industry to make various alloys
Different lanthanides are found together
in nature; difficult to separate because of
the similar properties
Actinides
Only thorium and uranium exist on
Earth in any significant amounts
 Uranium: used in nuclear power
 All elements after uranium were
created artificially in a laboratory.
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Nonmetals
Lack most of the properties of
metals
 Located to the right of the
zigzag line
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Physical Properties
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In general: opposite of metals
Gases at room temperature; means they have
low boiling points
Dull
Solid nonmetals are brittle.
NOT malleable or ductile
Lower densities than metals
Poor conductors of heat and electricity
Chemical Properties
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Readily form compounds; except Group
18
Group 18 elements do not react with
other elements.
Many form molecules containing 2
atoms: diatomic molecules (O2)
Nonmetals can form compounds with
metals (NaCl) or other nonmetals (CO2).
Families of Nonmetals
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Carbon Family (Group 14)
 All have 4 valence electrons.
 Carbon is the only nonmetal in the
group.
 2 are metalloids; 2 are metals
 Carbon is special because it is
important for life. ALL living things
contain Carbon!
Families of Nonmetals
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Nitrogen Family (Group 15)
 All have 5 valence electrons.
 Only 2 nonmetals in this group: nitrogen &
phosphorus
 N2 makes up about 80% of our air; most
living things can not use it in gas form
 Get nitrogen from food
 Phosphorus is not a stable element; always
found in compound in nature.
 Used to make matches and flares
Families of Nonmetals
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Oxygen Family (Group 16)
 All have 6 valence electrons.
 Elements typically gain or share 2 electrons
 Oxygen we breathe = O2
 Ozone = O3
 Oxygen is very reactive and can combine easily
with other elements.
 Oxygen: most abundant element in Earth’s crust;
second most abundant in the atmosphere
 Sulfur is a common nonmetal in the Oxygen family
Families of Nonmetals
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Halogen Family (Group 17)
 All have 7 valence electrons.
 All but Astatine are nonmetals; Astatine is a metalloid
 Typically gain or share 1 electron
 ALL are very reactive; most are dangerous to humans
 Compounds that they form are useful:
 Flourine—toothpaste, nonstick cookware
 Chlorine—table salt
 Bromine—reacts with silver (photographic film)
Families of Nonmetals
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Noble Gases (Group 18)
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Also known as inert gases
ALL have 8 valence electrons
Do Not ordinarily form compounds
Do not gain, share, or lose electrons; very stable
and unreactive
All exist in Earth’s atmosphere, but only in small
amounts
Families of Nonmetals
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Hydrogen
 Simplest of all elements
 Generally contains only one proton and one electron
 Cannot be grouped in a family because its chemical
properties are so different from other elements
 Makes up 90% of the atoms in the universe; only 1% of
the mass of Earth’s crust, oceans, & atmosphere
 Rarely found on Earth as an element
 Mostly combined with oxygen (water)
Metalloids
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On zigzag line between metals & nonmetals
7 elements
Some have characteristics of metals; some
have characteristics of nonmetals
Most useful property is their varying ability to
conduct electricity
Most common is silicon
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Sand, glass, cement
Metalloids
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Whether they conduct electricity depends on
temperature, exposure to light, or presence of
impurities
Semiconductors: substances that under
certain conditions can carry electricity, while
under others it cannot
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Silicon & germanium
Used to make computer chips, transistors, lasers