Transcript Ch.4 Notes - Green Local Schools

The Periodic Table
Ch.4
(4-1) Johann Dobereiner
• Law of Triads: groups of 3 elements w/
similar properties
Li
Ca
Cl
Na
Sr
Br
K
Ba
I
John Newlands
• Inc. atomic mass
• Law of Octaves: properties repeated w/
the 8th element
Li
Be
B
C
N
O
F
Na
Mg
Al
Si
P
S
Cl
Dmitri Mendeleev
• Modern periodic system
• Inc. atomic mass
• Elements of similar properties fall in
vertical columns
– Don’t always fit in inc. mass (Te, I)
– Gaps where particular mass should fit
Henry Moseley
• Arranged elements in order of inc.
atomic #
Periodic Law
• Properties of elements are periodic
functions of their atomic #’s
– Regular repeating pattern
Periods & Groups
• Period: horizontal row
– Similar e- config.
• Group (family): vertical column
– Similar properties
Metals
• Metal: good conductor of electricity
• Transition metals:
– d & f-block
– Not as reactive as Gr.1 & 2
Nonmetals & Metalloids
• Nonmetal: poor conductor of electricity
– Some of p-block
• Semiconductor (metalloid): conduct
electricity, but not well
– Along stair-step (B, Si, Ge, As, Sb, Te)
Main Group Elements
• Representative elements
• Regular e- config.
• s- & p-block
s
p
Gr.1 – Alkali Metals
•
•
•
•
Very reactive metals
1 e- in highest E level
Burn in air
Extremely soft
Plasma
• 4th state of matter
• Mixture of particles that conducts
electricity
Gr.2 – Alkaline-Earth Metals
• Reactive metals (less than Gr.1)
• 2 e- in outer E level
• Harder & stronger than Gr.1
Lanthanides
• Shiny transition metals
Actinides
• Shiny transition metals
• Radioactive (unstable nucleus)
Gr.13 – Boron Family
• Metalloid & metals
• Al used to be rare & expensive
Gr.14 – Carbon Family
• Elements impt. to life (C) & computers
(Si & Ge)
Gr.15 – Nitrogen Family
• N2 makes up ¾ of atmosphere
• N & P impt. to life
Gr.16 – Oxygen Family
• O2 necessary for respiration
• Many stinky things contain S (rotten
eggs, garlic, skunks)
Gr.17 - Halogens
• Most reactive of nonmetals
• 7 e- in the outer E level
• Combine w/ metals to form salts
– Ex: K+ + Cl-  KCl
– Salt: + & - ions arranged in a regular 3-D pattern
(crystal)
Gr.18 – Noble Gases
• Very low reactivity
• Very stable
– 8 e- (octet) in outer E level
Hydrogen
• Most common element
• Reacts w/ many elements
• Alternative fuel source
(4-2) Characteristics of Metals
• Shiny (luster)
• Good conductors
• e- free to move through a metal in all
directions
– Sea of e-
Characteristics of Metals
• Ductile: drawn into a wire
• Malleable: hammered or rolled into
sheets
• Alloy: solid or liquid soln of 2 or more
metals or sometimes nonmetals
Symbols
• Metals will be in a crystal form attached
to many other metal atoms
• Monatomic symbols: Fe, Hg,etc.
(4-3) Periodic Trends
• Bond radius: ½ the dist. from the center
of 2 like atoms bonded together
Atomic Radius
• Inc. down a group
– Add extra E levels
– e- shielding: reduction of attractive force
b/w a + nucleus & outer e- due to
cancellation of some + charge by inner e-
• Dec. across a period
– Inc. + charge of nucleus & pull e- closer
Ionic Radius
• Ions aren’t the same size as the atoms
they come from
• + ions are smaller
– Lose layers of e-
• - ions are larger
– Gain layers of e-
Ionization Energy
• Amt of E needed to remove an outer ein its ground state
• Inc. across a period
– + charge inc. which holds e- more tightly
• Dec. down a group
– Outer e- farther from nucleus
Electron Affinity
• Ability of an atom to attract & hold an e• More negative across a period
– + charge inc. & attraction to e- inc.
• Dec. down a group
– Shielding offsets + charge & attraction to edec.
Melting & Boiling Points
• mp & bp reach their max when d & p
orbitals are ½ full then dec. again
p
d
(4-4) Big Bang
• 12-16 bya entire universe fit on pinhead
• Exploded, but T’s were so hot only E
existed
• Expanded, cooled, & atoms formed
• Clouds of H accumulated & gravity
pulled them closer together inc. P & T
forming stars
Natural Elements
• In hot center of stars, nuclear rxns took
place
• Nuclear rxn: change in the composition
of the nucleus of an atom
– Fusion
• The higher the T, the larger the element
formed
• 93 naturally occurring elements
Synthetic Elements
• Transmutation: changing 1 nucleus into
another by radioactive disintegration or
bombardment w/ other particles
Cyclotron & Synchrotron
• Cyclotron: accelerates charged
particles to very high E
– Forces fusion
• Synchrotron: times impulses to match
acceleration of particles
– Used for superheavy elements