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 8 th element LiBeBCNOF NaMgAlSiPSCl

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 sp

Gr.1 – Alkali Metals Very reactive metals 1 e - in highest E level Burn in air Extremely soft

Plasma 4 th 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 N 2 makes up ¾ of atmosphere N & P impt. to life

Gr.16 – Oxygen Family O 2 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 d p

(4-4) Big Bang 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