Chapter 6-7

The Periodic Table, Periodic Law, and The Elements

Periodic Table• Elements are

arranged in increasing atomic number according to similar properties in columns or groups

• It was developed over decades

• 1790’s- Lavoisier compiled a list with 23 elements

John Newland

• 1864- arranged elements by the “law of octaves”

• (1st arranged) – right idea but not exactly right after the first 14 or so.

Demitri Mendeleev (1834-1907)

• Russian• 1869- designed the

“modern table”

Moseley slightly rearranged based on atomic number and created our basic modern table

Periodic Law

• There is a periodic repetition of properties when arranged by atomic number

Groups

• Also called families (vertical columns)

• Share similar properties – End in same e-

configuration– Same valence e- – Same reactivity

Period

• Horizontal rows• Share same highest

energy level

Periodic trends

• Atomic radius- half the distance between the nuclei of identical atoms that are bound together – Group trend: increase down

Atomic radius increases down because as you go down there are more electrons and more energy levels and with each energy level you get further from the nucleus.

– Periodic trend: decrease left to right

Atomic radius decreases from left to right because when you go across a period electrons are being added to the same energy level, which makes a stronger attraction and pulls electrons closer to the nucleus resulting in a smaller atom.

Ionic radius

• Ion- has a charge (+ or -) – when an atom gains or loses an e-

• Cation- positive ion- lost e- - smaller than neutral

• Anion- negative ion- gained e- - larger than neutral

*** same trend as atomic radius

Ionization energy

• Energy required to remove an e-

• Each e- has its own energy

• 1st IE<2nd<3rd

• Group trend: decreases down

• Period trend: increases across

• These trends are both due to the fact that electrons are more difficult to remove from stable elements

Electron affinity

• Energy change that occurs when an e- is acquired by a neutral atom

• Fe + e- Fe-

Electronegativity

• Relative ability of an atom to attract electrons to itself in a bond

– Pauling electronegativity scale

– Period: increase left to right

– Group: decreases down

– General trend: increase up

and right

F=most electronegative

O=second most

Fr=least

Hydrogen and helium

• Unique- can both occupy 2 groups

• H= 1A & 7A• He= 2A & 8A

• 99% of Universe• 76% = H• 23% = He

Alkali Metals: groups 1 or 1A• Alkali comes from Arabic-

“ashes”• All are very reactive, react

violently with H2O, soft, low density, low melting pts.

• Li- batteries, dehumidifiers, bipolar disorder medication

• Li2CO3 -in glass, airplane parts• Na- salt, vapor lamps, heat

exchanger in nuclear reactors, electrolyte

• K- electrolyte for muscles, one of 3 main ingredients in fertilizer– KNO3 in large scale fireworks

and gun powder

Alkaline Earth metals: group 2 or 2A

• All but Be form oxides that will not melt and form basic solutions

• Less reactive than 1A• More dense, higher melting points• Be- with Al, Si, and O makes beryl

(emerald/ aquamarine), moderates neutrons in reactors, Be/Cu alloys are used for tools where no sparks can be formed like refineries

• Mg- backpack frames, bicycle wheels, “mag” wheels, oxide used to line furnaces, every chlorophyll has 1 Mg+2, muscle function and metabolism- found in “hard” H20 with Ca +2

Alkaline earth metals continued…

• Sr- crimson fireworks• Ba- paints, additive in

glass, diagnostic tool in medicine

• Ra- highly radioactive, once used in glow in the dark paint for watches

Aluminum Group: group 13 or IIIA

• B- metalloid, Borax is the name of the mined compound• B/Si/O=borosilicate=pyrex• Mined in the Mojave Desert

Boric acid: disinfectant, ant repellant

Boron nitride: second

hardest substance

Aluminum group continued….• Al- cans, foil• most abundant metal on

earth• 3rd most abundant element

on earth• Mined from bauxite

– Strengthens ceramics, heat- resistant fabric, ruby and sapphires are mainly Al2O3

– Al2(SO4)3- alum- antiperspirant and water purification

Al group Continued…..

• Ga- used in some thermometers from 30o to 2400oC– Gallium arsenide produce

photoelectric cells – Solar power=calculators– 10x more efficient than Si

chips– Gallium nitride- used for blue

lasers (can triple storage)

Carbon group: group 14 or IVA

• C- has its own study- organics – Exist in at least 4

natural forms – diamond, graphite, coal (soot), Buckminster fullerene

Carbon group Continued…..

• Si- computer chips, solar cells, 2nd most abundant element in the crust, most common form is silica, (Si02) A.K.A sand, glass, quartz– Silicon carbide-

industrial abrasive (carborundum)

Carbon group Continued….

• Ge- metalloid- solid state electronics

• Pb- toxic, was in paint, may have been 1st pure metal, additive in glass, causes brain damage

• Sn- coating for cans, Bronze, construction materials, foil

Nitrogen Group: Group 15 or VA

• N- colorless, odorless, unreactive-= 80% of air; compounds- fertilizer, explosives (TNT), DNA, Ammonia (cleaning), dyes, nitroglycerin – HNO3- used to etch metal plates

and other industrial uses

Nitrogen group continued..

• P- has 3 allotropes (white, red, black), phosphoric acid, processed cheese, laxatives, matchbox, baking powder, fertilizer, ATP, DNA, detergents

Nitrogen continued…

• As- toxic, Arsenic sulfide was used as medicine, metalloid

• Sb- antimony sulfide was used as a cosmetic to darken eyebrows and make eyes appear larger, 5% of modern Pb storage batteries, Sn/Sb alloy can be molded (tableware)- metalloid

Nitrogen Continued….

• Bi- Pepto Bismol, Bi/Pb/Sn/Cd alloy called woods metal used as a plug in sprinkler system

Oxygen Group: group 16 or IVA

• O- 2 allotropes 02/03---most abundant element on earth

-bleaching agent

50% of earth crust= 20% of air

Oxygen Continued…

• S- 10 allotropes

-Cinnabar, galena

-can be found in nature in pure form (yellow)

H2S04= fertilizer production, steel, paper, paint

silver tarnish is H2S + AgAg2S

Oxygen continued…

• Se- works with Vitamin E to prevent cell damage, can be toxic= RDA= 10 g, toxic L050= /m3, can convert light to electricity- used in solar panels, photographer meters, photocopiers, semiconductors

• Te- metalloid- semiconductors- rare

• Po- named for Poland- rare, radioactive, toxic

Halogens: Group 17 or VIIA

• Most reactive nonmetals- “halo”- salt “genero”- form= salt formers

• State of matter at room temp.

• F, Cl= gas• Br= liquid• I, (At)= solid

Halogens continued….

• F- most electronegative element- most active element– “fluere”- latin, “to flow”-

added to H20 and toothpaste to prevent decay, teflon= F/C compound reacts with U to form gases (U enrichment) U-235

Halogens Continued…

• Cl- deadly gas in its pure form

-can be a disinfectant

-NaCl=bleach

-nerve blocker in medicine

HCl- removes rust or algae, etc. (muriatic)

-mixed with oil=PVC

(Poly Vinyl Chloride)

Halogens Continued…

• Br- photographic film

• I- photographic film, needed to maintain a healthy thyroid (controls growth and metabolic rate), disinfectant, iodized salt

• At- radioactive, man-made

Nobel Gases: group 18 or VIIIA

• All were considered inert (nonreactive) until the 1960’s

• He, Ne, Rn- still no

compounds

Noble gases continued…

• He- used in balloons, blimps, and dive tanks

-liquid form=coolant

-superconducting magnets

-pale yellow “neon” lights

• Ne- first “neon” light -bright orange

Noble gases continued…

• Ar- insulation in windows, 1% of air, blue “neon” light, atmosphere of incandescent lights, high temp. welding

• Kr- used as insulation in windows• Xe- 1st to form a compound • Rn- deadly radioactive gas from U

decay, found under homes

Transition metals

• D-block- groups 3-12 – B elements

• Various uses and forms -Cobalt 60=chemotherapy -Fe= construction -Fe, Co, Ni= magnets -Ag, Au, Pt= “precious” metals -Cu= wire -Co= red blood cells -Mn= cell respiration

Inner transition metals

• The “f” block• Lanthanide and actinide series• Ce= used to remove C from

steel, movie projectors, search lights

• Pu= 239 reactor fuel• Am= smoke detectors • Nb, Pr= welding goggles• Yb, Eu= TV screens, computer monitors