Transcript Periodic Table of the Elements

Groups of the Periodic Table
Aim PT3 – what are the
characteristics of the different
groups (also known as FAMILIES) in
the Periodic Table?
Hydrogen
• Hydrogen belongs to a
family of its own.
• Hydrogen is a diatomic
reactive gas.
• Diatomic molecule are elements that occur
in nature in pairs - Br I N Cl H O F
• Remember the Hindenburg!
• Hydrogen is promising as an alternative
fuel for automobiles
Group 1 - Alkali Metals
• 1st column on the periodic table
(Group 1) not including hydrogen
• One (1) electron in valence shell
• Very reactive metals, always
combined with something else in
nature (like in salt) (go to vid)
• Soft enough to cut with a butter
knife
• Examples
– Lithium (Li)
– Sodium (Na)
– Potassium (K)
Group 2 Alkaline Earth Metals
• Two (2) electrons in valence
shell
• Reactive metals that are always
combined with nonmetals in
nature
• Several of these elements are
important mineral nutrients
• Examples:
– Magnesium (Mg)
– Calcium (Ca)
Group 3 – 12 - Transition Metals
• All have mobile electrons
– Two outer shells allow electrons to
move back and forth between them
– allows heat and electricity to pass
through metals easily
• Less reactive, harder metals than
Group 1 or 2
– Form colored solutions when mixed
with water
– High melting points
• Includes metals used in jewelry and
construction
Group 13 - Boron Family
• Three (3) electrons in
valence shell
• Examples
– Aluminum metal was
once rare and
expensive, not a
“disposable metal”
– Boron – used in nuclear
fission reactors as a
neutron moderator
Group 14 - Carbon Family
• Four (4) electrons in valence
shell
• Contains elements important
to life and computers.
• Carbon is the basis for an
entire branch of chemistry
called organic chemistry
• Silicon and Germanium
– important semiconductors
Group 15 - Nitrogen Family
• Five (5) electrons in the valence shell
• Nitrogen makes up over ¾ of the
atmosphere
• Nitrogen and phosphorus are both
important in living things
– Most of the world’s nitrogen is not available to
living things
– Legumes (beans and peanuts) contain nitrogen
fixing bacteria so that it is available to plants
• Two thirds of the earth’s population dependent
on nitrogen fixing bacteria for their food
Groups 16 - Oxygen Family or
Chalcogens
• Six (6) electrons in the valence
shell
• Oxygen
– Molecular oxgyen (O2 ) is
necessary for respiration
– Ozone (O3 ) protects us from
UV radiation
• Many things that stink, contain
sulfur
• Ex: rotten eggs, garlic, skunks, etc.
Allotropes
• Elements with
– different physical
properties
– But same chemical
composition
• Examples
– Carbon – two forms
– Oxygen – two forms
– molecular oxygen and
ozone
Group 17 - Halogens
• 7 electrons in valence
• Very reactive, volatile,
diatomic molecule
• Always found combined
with other elements in nature,
like salts
• Used as disinfectants and to
strengthen teeth
– Flouride in water, toothpaste
– Chlorine bleach, tabs for pool
– Iodine in antiseptics
Group 18 - The Noble Gases
• A full set of 8 electrons in the
valence shell
• VERY unreactive, monatomic
(only atom per molecule)
molecular gases
• Helium – balloons and blimps
• Neon – the glowing signs we
all love
• Argon – incandescent
bulbs