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Periodic Law
• Do Now:
What does an element’s position on the
periodic table indicate about its properties?
Organizing the Elements
• Cu, Ag, Au are three of the oldest known
elements.
• By the year 1700, only 13 elements had been
identified and isolated.
• From 1765-1775, five new elements including
H, N, and O had been isolated.
• As soon as elements were (are) identified,
scientists begin to look for similarities and
classify them.
Classifying Elements
• JW Dobereiner published a classification system
in 1829.
– Elements grouped in triads (3 elements with similar
properties)
– Couldn’t group all elements using that system
• Dmitri Mendeleev published a table of elements
in 1869
– Organized in order of increasing atomic mass
• Mendeleev
When classifying elements, Mendeleev organized
according to atomic mass.
He left spaces where undiscovered elements
would most likely fit.
As these elements were discovered, their
properties nearly matched those he predicted.
His table gained widespread acceptance.
Mendeleev’s Table
The Periodic Law
• In developing the Periodic Table, Mendeleev
noticed problems.
• Atomic mass order didn’t always match
periodic trends.
• The table was eventually rearranged according
to atomic number.
In the modern periodic table, elements
are arranged in order of increasing
atomic number.
• periodic tables
Rows or Periods
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7 rows (called periods) on the periodic table
Period 1 has 2 elements
Period 2 has 8 elements
Period 4 has 18 elements
Period 6 has 32 elements
Each period corresponds to a principle energy level
Higher periods have more elements because there
are more orbitals in higher energy levels
Columns or Groups
• Groups have similar properties.
• Properties change across a period but those
properties repeat as you move from period to
period
• Periodic Law: when elements are arranged in
order of increasing atomic number, there is a
periodic repetition of their physical and
chemical properties.
• The properties of an element
are similar to those of other
elements in the same group.
Periodic Law:
• When elements are arranged in
order of increasing atomic
number, there is a
of their physical and
chemical properties.
•
• Horizontal rows =
are 7 periods
• Vertical column =
•There
(or family)
–•Similar physical & chemical prop.
–•Identified by number & letter (IA,
IIA…)
Metals, Nonmetals, Metalloids
• 3 broad classes of elements
• Across a period, elements
become less metallic, and
more nonmetallic
Metals, Nonmetals, and Metalloids
Basic Properties of Elements
Metals
• 80% of all
elements
• Conduct heat
and electricity
• High luster or
sheen
• Solid at room
temp (except Hg)
• Ductile
• malleable
Nonmetals
• Most are gases
• Some solids
• Br is a liquid at
room temp.
• Properties
opposite to
those of metals
Metalloids
• Located on stairstep line
• Properties of
metals and
nonmetals
• Very useful
because of ability
to control
properties
Metals
• 80% of the elements are
considered to be metallic
• Freshly cut metals have high luster
• All metals are solid at room temperatureexcept Hg
• Most metals are ductile and malleable
(can be drawn into wires and hammered into
thin sheets)
Nonmetals
• MOST nonmetals are gases at room
temperature
• Some are solids (carbon, sulfur, etc)
• One is a liquid- bromine
Poor conductors of electricity
Exception-carbon
Metalloids
• “stair step” line separates metals from
nonmetals-the elements along this line
are known as metalloids
• Have properties similar to metals and
nonmetals
• Chemists do not always agree on which
elements to classify as metalloids
• http://www.ehow.com/info_8675759_usesmetalloids-industry.html
Do Now
• Which of the following is least likely
to be a metalloid?
• A. As
• B. Hg
• C. Ge
• D. Si
• E. Sb
Do Now
• Chemical properties of the elements
are defined by the
• A. Electrons
• B. Ionization energy
• C. Protons
• D. Neutrons
• E. electronegativity
Classifying Elements
• Squares in the Periodic Table tell us:
–Atomic #
–Element name-black/solid, gases/red,
blue/liquid
–Average atomic mass
–Vertical column of numbers in the top
right corner-number of electrons in
each occupied energy level
Sort Elements based on Electron
Configuration
–Noble gases- s and p sublevels full
ex: Ar 1s22s22p63s23p6
Representative elements- Group 1A-7A
group #=# of electrons in highest
occupied energy level
Classifying the elements even
further…..by group (column)
Groups
• Every group has the same number of valence
electrons
• Can be represented by Lewis Dot Diagram
• Lewis Dot Diagram – represents the valence
electrons by placing dots around the element
symbol
Lewis Dot Diagrams
• Draw the Lewis Diagram for the following:
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Lithium
Beryllium
Boron
Carbon
Nitrogen
Oxygen
Fluorine
Neon
• In a chemical reaction, the
outermost electrons make first
contact – this is why elements
with similar electron structures
have similar chemical
properties
Family (Group) Names
• Group I - Alkalai metals
Alkalai Metals
• Highly reactive - found in nature only as
compounds
• Reactivity increases from the top of the group
to the bottom
• http://www.periodicvideos.com/
Family Group Names
• Group II – Earth metals
Group II Earth Metals
• Differences in reactivity among the earth
metals are shown by the ways they react with
water
• Increasing reactivity from top to bottom
within a group
Transition Metals
• Transition metals-have electrons in the d
orbitals
–Inner transition metals- have electrons
in the f orbital
Family Group Names
• Group III – Boron group
Group III Boron Group
• Aluminum is the most common element in
this group and is the most abundant metal in
the Earth’s crust
Family Group Names
• Group IV – Carbon group
Group IV Carbon Group
• Electrical conductivity increases from top to
bottom within a group
• Most compounds in your body contain carbon
• Compounds of silicon and carbon are
extremely hard and used to coat saw blades
Family Group Names
• Group V – Nitrogen group
Group V Nitrogen Group
• Nitrogen and Phosphorus are the most
common group 5 elements
• Nitrogen and phosphorus are used in
fertilizers
• White phosphorus highly reactive, red
phosphorus used to make matches ignite
• phosphorus
Family
Group Names
• Group VI – Oxygen group (Chalcogens)
Group VI Oxygen Group
• Oxygen is the most abundant element in the
Earth’s crust
• Pure oxygen is flammable
• Sulfur was one of the first elements to be
discovered – used to produce sulfuric acid
• http://www.boston.com/bigpicture/2009/06/
sulfur_mining_in_kawah_ijen.html
Family Group Names
• Group VII – Halogens
Group VII Halogen Family
• Highly reactive nonmetals
• Chlorine used in pools and bleach
• Fluorine used in toothpaste
• Thyroid gland needs iodine to work properly ,
added to table salt
Family Group Names
• Group VIII – Noble Gases
Group VIII Noble Gases
• Colorless, odorless gases, extremely
Unreactive
• Some light bulbs are filled with argon to
increase life of the bulb
Do Now
• A solid element has 2 valence electrons.
That element must be
• A. A halogen
• B. A noble gas
• C. A radioactive element
• D. an alkalai metal
• E. An alkaline earth metal
Do Now
• Which pair of elements is expected to
have the most similar properties?
• A. Potassium and lithium
• B. Sulfur and phosphorus
• C. Silicon and carbon
• D. Strontium and barium
• E. Fluorine and iodine
Periodic Law:
• When elements are arranged in
order of increasing atomic
number, there is a
of their physical and
chemical properties.
•
Trends in Atomic Size
• The electron “cloud” does not have an
edge, it is a probability…so how can we
measure how large these atoms are?
• Measure more than one at a time
• Atomic radius– how we measure the size of an atom–defined as half the distance between 2
nuclei of a diatomic molecule
Nucleus
Atomic radius
Total Distance
between 2 nuclei
Trends in ELECTRONEGATIVITY
• Electronegativity-the tendency for an atom to
attract electrons to itself when it is chemically
combined to another element
• An atom with a large electronegativity means
it pulls electrons towards itself
Electronegativity, 
 is a measure of the ability of an atom in a
molecule to attract electrons to itself.
Concept proposed by
Linus Pauling
1901-1994
Electronegativity
Which is more electronegative?
• F or Cl ?
• Na or K ?
• Sn or I ?
• Within a
the farther
down the group,
`
the farther away the electron is from the
nucleus, low electronegativity
• Within a
metals are on the left, they
let their electrons go easily- low
electronegativity
• Nonmetals on the right, they want more
electrons – high electronegativity
• Summary of Electronegativity trend…
• Electronegativity increases from left to
right across a period
• Electronegativity decreases from top to
bottom within a group
Trends in DENSITY
• increases from top to bottom within
a group due to smaller change in
atomic size and a large change in
atomic mass
Trends in Melting points and boiling
points of metals
• decrease from top to bottom
within a group – due to atomic
size
Melting Points and Boiling points of
nonmetals
• increase from top to bottom
within a group
• Due to atomic size/nuclear
charge
Do Now
• The best way to estimate the boiling point
of Pd is to
• A. Average the bp of Rh and Ag
• B. Average the bp of Ni and Pt
• C. Average the bp of Ir and Cu
• D. Average the bp of Co and Au
• E. None of these will work
Trends in Metallic character
Increases from top to bottom
within a group
• Decreases from left to right
across a period
The End !!!!!!!!!!!!!!!!!!!