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Periodic Table
• The Periodic Table of Elements is the most
important reference in chemistry, and it
represents all the known chemical
elements as well as those that are yet to
be discovered. The elements are arranged
in a systematic order to show their
patterned recurring or ‘periodic’ chemical
and physiological properties. Currently,
there are a total of 117 elements in the
standard periodic chart.
PERIODIC TABLE
• COLUMNS (GROUPS/FAMILIES) —
vertical (* have similar but not identical
properties) (atomic size increases from
top to bottom)
• PERIODS — horizontal rows —
Certain properties of elements vary
in regular ways from left to right
across a period. These properties
include electron arrangement,
reactivity, atomic size, and metallic
properties.
• FAMILY 1 (ALKALI METALS)
–Exception Hydrogen
–Single electron in outermost energy
level
– 1 valence electron (+1)
–Soft, silver-white, shiny metals
–Good conductors of heat and electricity
–Very reactive (never found as free
elements)
• FAMILY 2 (ALKALINE EARTH
METALS)
–Never found in nature as an
uncombined elements
–Two electrons in outermost energy
level
–2 valence electrons (+2)
–Not as reactive as the alkali metals
• FAMILIES 3 TO 12 (TRANSITION METALS)
– Do not fit into any other Family
– Properties similar to one another but different
from other Families
– Good conductors of heat and electricity
– Brightly colored (paints)
– Most have 1 or 2 valence electrons
– Lose either 1 (+1) or both (+2) BUT can
also lose an electron from the next - outermost energy level
– Sometimes can share electrons when they
form bonds with other atoms
– Form so many different compounds
to
Transition Metals
• Transition metals are like main group metals
in many ways: They look like metals, they are
malleable and ductile, they conduct heat and
electricity, and they form positive ions. The
fact the two best conductors of electricity are
a transition metal (copper) and a main group
metal (aluminum) shows the extent to which
the physical properties of main group metals
and transition metals overlap.
Transition Metals
• There are also differences between
these metals. The transition metals are
more electronegative than the main
group metals, for example, and are
therefore more likely to form covalent
compounds.
Transition Metals
• Another difference between the main group metals
and transition metals can be seen in the formulas of
the compounds they form. The main group metals
tend to form salts (such as NaCl, Mg3N2, and CaS) in
which there are just enough negative ions to balance
the charge on the positive ions. The transition
metals form similar compounds [such as FeCl3,
HgI2, or Cd(OH)2], but they are more likely than main
group metals to form complexes, such as the FeCl4-,
HgI42-, and Cd(OH)42- ions, that have an excess
number of negative ions.
• FAMILY 13 (BORON FAMILY)
–Three electrons in outermost energy
level
–3 valence electrons (+3)
–One metalloid (BORON) / others
metals
METALLOIDS
• A metalloid is an element with properties
that are in between, or a mixture of, the
properties of metals and nonmetals and
thus is hard to classify as either a metal or
a nonmetal.
METALLOIDS
• Metalloids are the elements found along the stair-step
line that distinguishes metals from non-metals. This line
is drawn from between Boron and Aluminum to the
border between Polonium and Astatine. The only
exception to this is Aluminum, which is classified under
“OTHER METALS". Metalloids have properties of both
metals and non-metals. Some of the metalloids, such as
silicon and germanium, are semi-conductors. This
means that they can carry an electrical charge under
special conditions. This property makes metalloids useful
in computers and calculators
Semiconductors
• Also called metalloids
• Not metals but have the some properties
of metals
• Ability to conduct heat and electricity
under certain conditions
• Si: used in computers and electronic
devices
• B: increases strength of steel
• Sb: used as a fire retardant
• FAMILY 14 (CARBON FAMILY)
–Four electrons in outermost energy
level
–4 valence electrons
–Carbon (nonmetal) / Si + Ge
(metalloids) / Sn + Pb (metals)
• FAMILY 15 (NITROGEN FAMILY)
–Five electrons in outermost energy
level
–5 valence electrons (-3)
–Tend to share electrons when they
bond with other atoms
• FAMILY 16 (OXYGEN FAMILY)
–Six electrons in outermost energy
level
–6 valence electrons (-2)
–Most elements in this Family share
electrons when forming compounds
• FAMILY 17 (HALOGENS)
–Seven electrons in outermost energy
level
–7 valence electrons (-1)
–Tend to GAIN only 1 electron to fill
their outermost energy level
–Very reactive
–Never found free in nature
–React with metals to form salts
Fluoride
• Fluoride is a mineral that occurs naturally in many foods
and water. Every day, minerals are added to and lost
from a tooth's enamel layer through two processes,
demineralization and remineralization. Minerals are lost
(demineralization) from a tooth's enamel layer when
acids -- formed from plaque bacteria and sugars in the
mouth -- attack the enamel. Minerals such as fluoride,
calcium, and phosphate are redeposited
(remineralization) to the enamel layer from the foods and
waters consumed. Too much demineralization without
enough remineralization to repair the enamel layer leads
to tooth decay.
Fluoride
• Fluoride helps prevent tooth decay by making
the tooth more resistant to acid attacks from
plaque bacteria and sugars in the mouth. It also
reverses early decay. In children under 6 years
of age, fluoride becomes incorporated into the
development of permanent teeth, making it
difficult for acids to demineralize the teeth.
Fluoride also helps speed remineralization as
well as disrupts acid production in already
erupted teeth of both children and adults.
Fluoride
• Hexafluorosilicic acid (systematically
named oxonium
hexafluorosilanediuide and oxonium
hexafluoridosilicate is an inorganic
compound. It is commonly used as a
source of fluoride for water flouridation.
• FAMILY 18 (NOBLE GASES)(INERT
GASES)
–Two/eight electrons in outermost
energy level
–2 valence electrons (Helium)
–8 valence electrons (all others)
–Normally unreactive
• RARE EARTH ELEMENTS
–LANTHANOID SERIES
–ACTINOID SERIES
• All radioactive
Rare Earth Elements
1. any of a group of chemically similar
metallic elements comprising the
lanthanide series and (usually) scandium
and yttrium. They are not especially rare,
but they tend to occur together in nature
and are difficult to separate from one
another.
• CLASSIFICATION OF ELEMENTS
– METAL: element that is a good conductor of
heat and electricity, is shiny, has a high
melting point, is ductile and malleable, and
tends to lose electrons.
– NONMETAL: element that is a poor
conductor of heat and electricity, has a dull
surface, low melting point, is brittle, breaks
easily, and tends to gain electrons.
– METALLOIDS: element that has properties
of both metals and nonmetals.
• CLASSIFICATION OF ELEMENTS
–LEFT— metals (tend to lose
electrons)
–RIGHTS — nonmetals (tend to gain
electrons)
–METALLOIDS — properties of both
metals and nonmetals (either side of
zigzag line)
• CLASSIFICATION OF ELEMENTS
– Left to Right
– Valence number charges
(+1,+2,+3,+4,-3,-2,-1,0,)
– Amount of energy needed to remove
electrons shows periodic increase
– Atomic size decreases
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– Becomes less metallic
Semiconductors
• Also called metalloids
• Not metals but have the some properties
of metals
• Ability to conduct heat and electricity
under certain conditions
• Si: used in computers and electronic
devices
• B: increases strength of steel
• Sb: used as a fire retardant