the periodic table ch.4. (4-1) johann dobereiner law of triads: groups of 3 elements w/ similar...
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The Periodic Table
Ch.4
(4-1) Johann Dobereiner
• Law of Triads: groups of 3 elements w/ similar properties
Li
Na
K
Ca
Sr
Ba
Cl
Br
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 e- in 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 e-
dec.
Melting & Boiling Points
• mp & bp reach their max when d & p orbitals are ½ full then dec. again
dp
(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