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

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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