Periodic Table
Elements are organized by:
 Atomic number
o Increasing atomic number and mass
 Similar chemical and physical properties
Symbol – unique to each element
Atomic Number
 # of protons and # of electrons
 Unique to each element – change the proton you
change the element
Atomic Mass
 Average # protons and neutrons in a specific
amount (6.03 x 1023atoms)
Rows = periods, there are 7 total!
 Elements in the same row DO NOT share similar
properties
 All elements in the same period have the same # of
electron orbitals/clouds/energy levels
o Row 1 = 1 orbital
o Row 5 = 5 orbitals
 # of rows helps to explain the size and reactivity of
an element
o More rows = bigger atom = more reactive
Columns = groups or families, there are 18 total!
 Usually represents the number of electrons in the
outer most shell – valence electrons
o Exception – transition metals
 # of valence electrons determines an elements
physical properties and how it will behave in a
chemical rxn.
 Elements within the same column exhibit very
similar properties
 Elements in the same column form the same
charged ion – exception transition metals
Important Families!
Hydrogen
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Only 1 member
Charge of ion = +1 (usually)
Diatomic (never alone in nature)
Reactive gas
Alkali Metals (group 1)
 Charge of ion = +1
 One valence electron
 VERY reactive metals (react violently with water)
– always combined in nature
 Soft enough to cut with a knife
Alkaline Earth Metals (group 2)
 Charge of ion = +2
 Two valence electrons
 Reactive metals are always combined with
nonmetals in nature
 Several are important nutrients
Transition Metals (group 3-12, etc)
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Charge of ion varies
Less reactive and harder
Good conductors of electricity and heat
Metals used as “metals”
Compounds are often brightly colored
Rare Earth Metals
 Lanthanide and Actinide series
 Actinides ae mostly man-made
 Similar to transition metals (often referred to as
“inner transition”)
Boron Family
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Charge of ion = +3
Three valence electrons
Most are metals (B is a metalloid)
Includes Al – most abundant elements in earth’s
crust
Carbon Family (group 14)
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Don’t form ions (usually)
4 valence eTends to share e- in bonds
Has metals, non-metals, and metalloids
2nd most stable group
Nitrogen Family (group 15)
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Charge = 35 valence eTends to share e- in bonds
Has metals, non-metals, and metalloids
Chalcogens (group 16)
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Charge = 26 valence eTends for share e- in bonds
O and S (elements responsible for stinky stuff)
Halogens (group 17)
 Charge of ion = 1 7 valence electrons
 Most reactive non metals – NEVER found free in
nature
o F can dissolve glass
 Diatomic and volatile
 Form “salts” with alkali/earth metals
Noble Gases (group 18)
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Don’t form ions
Full outer shell (8)
All other atoms want to be them
UNREACTIVE, monoatomic gases
Staircase indicates metalloids (exception Al)