Periodic Table of the Elements (PT) Flashcards
Alchemists
found (Au, Ag, Cu) knew earth/air/fire/water weren’t the only elements
Antoine Lavoisier
“Father of modern chemistry,” 1780 list of elements→ in order of density
Job Döbereiner
noticed Li, Na, K (violently explosive in H2O) had similar properties, Cl, Br, I (germ killers) had similar properties, & Cu, Ag, & Au had similar properties → “Triads” –nature organized into threes
Then… more elements were discovered and led to the creation of “groups” of elements
John Newlands
British classical pianist saw octaves and was made fun of by scientists because music & science was ☹ at the time. The octaves were periodic repetition → “periods”
Lothar Meyer (German) Dimitri Mendeleev (Russian)
took ≈ 60 known elements & made a table, published a PT of Elements
Mendeleev got credit because he published his in 1869 even though Meyer probably found it a little earlier. He also got credit because he FILLED in the BLANKS for 3 elements (based on atomic mass)! –later found to be Gallium, Germanium, and Scandium
How was the original PT arranged?
There is a repetition of properties of elements when listed in increasing atomic MASS.
Tellurium error
Te I, should be switched to I Te
Henry Moseley
Used an x-ray gun to count protons, fires x-rays through
and corrects Mendeleev.
How are elements in the PT listed?
There is a repetition of properties of elements when listed in increasing atomic NUMBER
Atomic radius across the PT
As you go from L → R across the PT, atomic radius decreases shielding e- stay the same, but net nuclear charge increases, pulling in the e- closer
Atomic radius increases going down, decreases L → R
Ionization energy:
energy needed to extract (yank off) an e- (INCREASE L→R, DECREASE T→B)
Electronegativity
affinity for e- (in a bond), directly related with atomic radii
F has a stronger desire for e- than O….
The PT is geographic
Louis Pauling
(UCLA) 2 Nobel prizes- Chemistry and Physics
look at diagram in reference word doc
