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PERIODIC TABLE
Chapter 5
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ORGANIZING THE ELEMENTS
Section 1
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LET’S REVIEW!
• Chemical properties
• Any property that can only be tested by changing the
chemical make-up of the substance.
• Physical properties
• Any property that can be tested without changing the
chemical make-up of the substance
• Atomic mass
• Mass of protons and neutrons
• Atomic number
• Unique to each element, same as number of protons
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DMITRI MENDELEEV
• 1870, there were 63
elements known to man
• He organized them in order
of their atomic mass, and
saw a pattern from their
properties.
• Was working on this while
Thomson and Rutherford
were still “exploring” the
atom
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DMITRI MENDELEEV
• Arranged his table with repeating properties in
columns, starting a new row each time the
chemical properties repeated
• Left blank spaces in his table, concluding that these
spaces were elements that hadn’t been discovered
yet.
• Based on the patterns and the other elements
around the blank space, he predicted the
properties of those elements
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AN EXAMPLE
What he called ekasilicon – it was discovered a few years later
Prediction
Germanium
Atomic Mass
72 amu
72.6 amu
Density
5.5 g/mL
5.3 g/mL
Appearance
dark gray metal
gray metal
Melting Point
high melting point
937o C
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MENDELEEV’S TABLE
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DMITRI MENDELEEV
• Some problems arose…
• A few elements appeared to be slightly out of
place
• Mendeleev put them in the right place and said
their atomic masses were incorrectly measured
• However, he was actually arranging them by
the wrong number
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HENRY MOSELEY
• ~1910: Discovered atomic number
• He rearranged the periodic table by
this number and it fell into perfect
order
• Mendeleev’s table worked because
as the number of protons increase,
the atomic mass should increase,
however if there are fewer
neutrons it could decrease
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PERIODIC LAW
• Periodic Law: physical and chemical properties
of the elements are periodic functions of their
atomic numbers
• In other words, when the elements are
arranged by their atomic numbers, you
should see chemical and physical properties
repeating themselves
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ROWS
• Left to right – called periods
• Elements in the same
periods show a pattern
• As you move left to right,
conductivity and reactivity
change, and elements
become less metallic
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COLUMNS
• Top to bottom – called
groups
• Elements in a group have
similar chemical properties
• The elements in the same
group (column) have the
same number of valence
electrons
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EXPLORING THE PERIODIC TABLE
Section 2
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REMEMBER
• The periodic table is organized by
atomic number
• For a neutral atom, the number of
protons equals the number of
electrons
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VALENCE ELECTRONS
• The trends found in a
periodic table are a result of
electron arrangement,
specifically, the number of
valence electrons
• Valence Electron: electrons
in the outermost shell
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VALENCE ELECTRONS
• The group number of an element will tell you the
number of valence electrons it has
• Group 1 elements: 1 valence electron
• Group 2 elements: 2 valence e- ’s
• Skip the middle
• Group 13 elements: 3 valence e- ’s
• Groups 14-18 elements: 4, 5, 6, 7, and 8 valence e- ’s
respectively.
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WHY DO WE CARE ABOUT
ELECTRONS?
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ION
• A neutral, stable atom will have equal
protons and electrons
• When an atom gains/loses electron(s), the
atom is no longer neutral and has a charge
• It becomes an ion
• Ion: a charged atom
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ION
• Ionization: When atoms EITHER gain or lose
electrons
• All atoms want to have 8 valence electrons in the
outer shell – this would make their outer shell full
• Elements that are really close to having 8
electrons, desperately want to get there, and
tend to be the most reactive.
• Elements that are already “full” are considered
inert, they don’t react because they don’t need
to gain or lose electrons
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LET’S RECALL
• Protons = positive charge
• Electrons = negative charge
• p+ # CANNOT change, but e- # can
• So…
• If an atom GAINED electrons,
would they be more positive, or
more negative?
• If they LOST electrons?
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CATION
• Remember…group 1 elements have 1 electron in
their outer shell
• So…group 1 elements like to give up their single
electron
• This would make it more POSITIVE
• We call this a cation
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ANION
• Remember…elements in group 17
have 7 electrons in its valence
shell (it would like 8)
• So…it will accept an electron from
a “donor”
• This would make it more NEGATIVE
• We call this an anion
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LET’S PRACTICE
• Group 16
Give Up? or Gain?
• Group 13
Give Up? or Gain?
• Group 15
Give Up? or Gain?
• Group 2
Give Up? or Gain?
• Group 1
Give Up? or Gain?
• Group 17
Give Up? or Gain?
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CHARGES
• How do we know if an atom is an ion?
• We show it with an exponent
• Cations have a +, and anions have a –
• If an atom has gained 3 electrons
• It is more negative = Al3-
• If an atom has lost 3 electrons
• It is more positive =
Al3+
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THE PERIODIC TABLE
• It is divided into three major categories
• Metals
• Nonmetals
• Metalloids (semiconductors)
• These categories are based on general properties
and are further broken down into families
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• Metals are left of the “staircase”
• Nonmetals are to the right
• Metalloids share properties of both
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METALS
• Most elements are metals
• Like to give up their valence electrons
• Physical properties
• high luster (shiny), conductive (heat and electricity),
malleable (bendable), ductile (stretchable), high density,
high melting point
• All except Hg are solids at room temperature
• Chemical properties
• Most will react with oxygen
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NONMETALS
• Like to gain electrons
• Physical properties
• dull, don’t conduct, brittle, low density,
low melting points
• Like ashes (mainly carbon)
• Can be solid, liquid or gas at room
temperature depending on the element.
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METALLOIDS (SEMICONDUCTORS)
• Share properties of both metals and nonmetals
• Can be shiny or dull, conduct ok, ductile and
malleable or brittle
• These elements have become really important
because of the computer revolution
• Computer chips are made out of semiconductors
(normally Si)
• By position Al is a metalloid, but its properties
make it a light metal
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FAMILIES OF ELEMENTS
Section 3
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FAMILIES
• Families of elements have
similar properties
• Each family also has the same
number of valence electrons
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METALS
Alkali Metals, Alkaline-Earth Metals, Transition Metals
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ALKALI METALS
• Group 1 (excluding H)
• 1 valence e• Very reactive, especially with
water
• Soft, shiny white metals (can
be cut with a knife!)
• Low density (Li, Na, and K
float in water)
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HYDROGEN
• Hydrogen is in group 1 but is
not an alkali metal, because
it is only 1 proton and 1
electron (no neutrons)
• Its properties are closer to a
nonmetals than to a metal
• it is a colorless, odorless,
explosive gas with oxygen
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ALKALINE-EARTH METALS
• Group 2
• 2 valence e- ’s
• Silver colored, more dense
metals
• Not as reactive as alkali
metals, but still very
reactive metals.
• Magnesium is used in
flash bulbs
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TRANSITION METALS
• Groups 3-12
• 1 or 2 valence e- ’s
• Most are silver in color
• Somewhat reactive
• These are most metals you
are familiar with
• iron, gold, copper, zinc
and nickel
• Since they are not that
reactive they have more
everyday uses.
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TRANSITION METALS
• Two bottom rows are the
Lanthanide and Actinide series,
sometimes called
innertransition metals
• Lanthanide: also called rareearth metals
• Actinide: very radioactive and
not easily found in nature
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NONMETALS
Halogens, Noble Gases
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HALOGENS
• Group 17/7a
• 7 valence e- ’s
• All nonmetals (can be solid,
liquid or gas)
• Extremely reactive with alkali
metals
• Chlorine is added to water
as a disinfectant.
• The “chlorine” added to
pools is a compound
containing Chlorine, by
itself chlorine is a green
gas
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NOBLE GASES
• Group 18/8a
• 8 valence e- ’s (except Helium)
• Full outer shell of electrons
• All are gases
• Extremely non-reactive (inert)
• All found in the atmosphere
• “Neon” lights contain a variety
of Noble Gases
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OTHER NONMETALS AND
METALLOIDS
• Groups 13-16 contain both nonmetals
and metalloids
• Nonmetals: Oxygen, Nitrogen, Carbon,
Sulfur, Phosphorus, and Selenium
• Metalloids: Boron, Silicon, Germanium,
Arsenic Antimony, and Terellium
• The group is named by the first element
in the column
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BORON GROUP
• Group 13
• 3 valence e- ’s
• 1 metalloid, all others are metals
• All are solids at room temperature
• Aluminum is the most common
• it is actually the most abundant element
on the planet.
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CARBON GROUP
• Group 14
• 4 valence e- ’s
• 1 nonmetal, 2 metalloids, 2 metals
• all are solids
• Pure carbon can be diamonds, soot (ashes) or
graphite.
• Silicon and germanium are used for computer
chips
• Tin and lead are common metals
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NITROGEN GROUP
• Group 15
• 5 valence e- ’s
• 2 nonmetals, 2 metalloids, 1 metal
• All but nitrogen are solids
• Nitrogen makes up 78% of the air
• Phosphorus is in several compounds (soaps)
• Arsenic is a well known poison
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OXYGEN GROUP
• Group 16
• 6 valence e- ’s
• 3 nonmetals, 2 metalloids
• except oxygen, all are solid
• Oxygen makes up 21% of the air
• it is necessary for things to burn
• sulfur is a yellow rock, that can burn.
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