Transcript 9.periodic.trends

Catalyst:
• Begin working on the handout at the front.
• Make sure you look up the definition of Lewis
Dot Diagrams!
Groups or Families
• The physical and chemical properties of elements repeat in a
predictable way when atomic numbers are used, this is
called periodic law.
Comparison of Groups (Families)
Similarities
Differences
Chemical properties
Total number of electrons
Number of valence electrons
Atomic mass
Charge
Reactivity
Classes of Elements
• Three ways to classify the elements:
1.
2.
3.
Solids, liquids, and gases based on state at room temp
Those that occur naturally and those that do not
Metals, nonmetals, or metalloids (based off of general properties)
Metal
Nonmetal
Metalloid
Metals
Properties
• Good conductors of
electricity and heat
• Solids at room temp
(except for mercury)
• Most are malleable
(can be shaped)
Palladium
Metals
• Many are ductile (can
be drawn into thin
wires)
• Some are very reactive
• Some do not react
easily
Nonmetals
• Poor conductors of
heat and electricity
• Low boiling points
• Many are gases at
room temp
Nonmetals
• Solid nonmetals at
room temp are brittle
• Broad range of
reactivity
Sulfur
Metalloids
• Properties fall between
metals and nonmetals
Silicon
• Ability to conduct
electricity varies with
temp
Germanium
Group 1: Alkali Metals
• Single valence electron
(+1)
• Contains Li, Na, K, Rb,
Cs, Fr
• Like to give away e• Very reactive
• Found in nature only as
compounds
EXAMPLE:
Table Salt (Na + Cl)
Group 2: Alkaline Earth Metals
• Two valence electrons
(+2)
• Contains Be, Mg, Ca, Sr,
Ba, Ra
• Like to give away e• Harder than group 1
• Reactivity is temp
dependent
• Important for biological
functions
Calcium important for bones
Magnesium plays key role in
photosynthesis of green
leafy plants
Group 3: Boron Family
• Three valence
electrons (+3)
• Contains metalloid
Boron and Al, Ga, In, Tl
• Contains Aluminummost abundant metal Window Frames
in Earth’s crust
• Aluminum used for
many things
Gutters
Airplanes
Group 4: Carbon Family
• Four valence electrons (+4)
• Group contains nonmetal
(C), two metalloids (Si/Ge),
& two metals (Sn/Pb)
• Metallic nature increases
from top to bottom
• Except for H2O, most of the
compounds in body contain
Carbon
Silicon in form of SiO2
Silicon carbide on saw
blades makes longer
lasting
Group 7: Halogens
• 7 valence electrons
• Highly reactive
nonmetals
• Contains F, Cl, Br, I, At
Chlorine used to kill bacteria in pools
Fluoride in toothpaste to prevent tooth decay
• Though physically
different they’re very
similar chemically
Seafood is a good source of iodine
Group 8: The Noble Gases
• Outer shell of electron
cloud is full
• 8 valence electrons
except for He (2)
• Colorless and odorless
• Extremely unreactive
• Used in “neon” lights