Transcript Elements

Elements
The Periodic Table:
Why is it arranged this way?
What is an element?
• Elements: Simplest form of a
substance; cannot be broken down
further and keep its physical and
chemical properties
• Atoms are the smallest particle of an
element
• Basic building blocks of compounds
(2 or more elements combined
chemically)
• Make up all matter on earth
Individual elements
(“tiles”)
Atomic number
79
Au
Gold
196.967
Atomic mass
chemical symbol
common name
Period
• Numbered rows (on left side,
rows go across)
• equal to the number of
energy levels in an
atom
• Periods have a pattern to them:
• Number of protons increases from left to right
• Number of electrons increases left to right
• The amount of energy needed to remove
electrons increases from left to right
• The size of the atom decreases as you move left
to right
Groups (families)
• Numbered columns (1 thru 18)
• All elements in the group have
the same number of electrons in
the outer energy level
• Valence electrons = outermost electrons
• Elements in group react in
similar ways
The zig-zag line:
• Line in periodic table
• Separates 88 elements that are
metals: to left of line, nonmetals to
the right
Metals
• metals tend to lose electrons when
chemically bonded with other
elements
• Lose electrons easily (become
positive ions)
Properties of metals
• What are some physical properties of
metals?
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Shiny
Ductile: can be drawn into wire
Malleable: can be flattened into sheets
Conduct heat and electricity
• What are some chemical properties of
metals?
• Corrode : react with water (rust,
tarnish,…)
• React with nonmetals to form compounds
• To the right of the line in the
periodic table are nonmetals:
• Nonmetals physical properties:
• Dull
• Brittle
• Can be solids, gases, or liquids
• Nonmetal chemical
properties:
• Gain electrons easily so they
react with metals (Sodium
reacts with chlorine: sodium
chloride)
Metalloids
• On either side of line:
• Metalloids: act like both metals
and nonmetals
• Boron, Silicon, Arsenic
Specifics on Chemical
Groups or Families
• Group 1: Alkali Metals
• Physical properties:
• Soft, silver metals
• Have one outer electron
• Chemical Properties:
• Always combine with another element, never
found alone in nature
• Combine especially with group 17 (VIIA)
• Examples: Potassium, Sodium
• Movie of potassium
Alkaline metals
• Group 2: Alkaline Metals
• Physical properties:
• Good conductors, grayish white in color
• Have 2 outer electrons
• This makes them LESS reactive than group 1
• Chemical Properties
• not as active as group 1 but still very
reactive
• Combine easily with Oxygen in group 16
(VIA)
• Magnesium and Calcium
Halogens
• Group 17 (VIIA): Halogens
• Physical Properties
• Nonmetals
• Group with the only liquid nonmetal
element
• Chemical Properties
• Very reactive: need only one electron to
fill outer shell
• Form salts (sodium chloride,
sodium fluoride)
• Fluorine, chlorine, iodine
• (Some are sensitive to touch!)
Noble (inert) gases
• Group 18 (VIIIA): Noble Gases
• Physical Properties:
• Gases at room temperature
• Chemical Properties
• Do not react easily with anything
because the outer electron shell is
already full!
• Helium, Neon, Krypton, Radon
Summary
• Elements: simplest form of a substance
• Elements have an atomic number, atomic
mass, chemical symbol
• Grouped into families by how reactive the
outer electron shell is
• Periods are the rows across
• Families share the same properties