Organizing the Elements Ch. 3 Sec. 2
May 11, 2015
Organizing the Elements
Ch. 3 Sec. 2
Activity-Which is easier? Pg. 80Your time (seconds)
RANDOM ORDER
Your time (seconds)
ROWS
Why is the Periodic Why is the Periodic Table important to me?Table important to me?
most useful tool to a chemist
organizes lots of info. about all known elements
Pre-Periodic Table Chemistry … …was a mess!!! No organization of elements. Imagine going to a grocery
store with no organization!! Difficult to find information. Chemistry didn’t make sense.
Dmitri Mendeleev: Father of the Table
HOW HIS WORKED…
Put elements in rows by increasing atomic mass.
Put elements in columns by the way they reacted.
SOME PROBLEMS… He left blank spaces for
what he said were undiscovered elements. (Turned out he was right!)
He broke the pattern of increasing atomic weight to keep similar reacting elements together.
The Current Periodic Table Mendeleev wasn’t too far off. Now the elements are put in
rows by increasing ATOMIC NUMBER!!
Each square of periodic table incl:
element’s atomic number= # of protons in its nucleus
chemical symbol name atomic mass= avg. mass of
all isotopes of that element15.9994
Chemical symbol 1 or 2 letters ex: iron= Fe
Groups
columns aka families 18 groups eg: Group 15= nitrogen family each group has similar characteristics
Periods Horizontal rows 7 periods
Periodic Table Song by Tom Lehrer
YouTube video-Meet the Elements
Periodic Table Rap-YouTube http://www.youtube.com/watch?
v=cAnOUwPfHlk&feature=related