The Beginning of the Elementsand

Early Periodic Tables

Dr. M. HazlettMandeville High School

Where did the elements come from?• At the start of the universe (and what existed

before this no one really knows) the temperatures were extremely high – around

100 000 000 000 oK!• The universe was just a quark-gluon plasma• Scientists theorize that the universe was mostly

photons, neutrinos, anti-neutrinos with a small number of protons and neutrons

• Because everything was so dense, these particles collided with each other

• The collisions eventually caused three major results:

First, the universe reached thermal equilibrium

Electrons and positrons were constantly interacting and annihilating each other (E = mc2)

This process released photons (quanta of energy)

Protons and Neutrons began converting into each other

p+ + v n0 + e+

p+ + e- n0 + v

Since neutrons are slightly heavier, more energy was needed tochange protons into neutrons, and an inequality began in favorof proton forming rxns

This process is called Nucleosynthesis• So, due to the super high temperatures and density,

the e-, e+, p+, and n0 began to collide– They got close enough for the Strong Force to take over

allowing nuclei to form• The first element was the nucleus of an isotope of

Hydrogen, Deuterium (2H) – a p+, n0

• This was joined by a p+ and formed 3He• Then, with another n0, 4He formed

(the stable form)• With the capture of free e-, a stable atom was made

The elemental fusion process begins• It all started with loose particles, and then H• From this start, He formed through fusion• Then the process took off – well, actually

taking millions and billions of years. . . . .

3He+2 + 4He+2 7Li+3 + e- + ϒ or 7Be+4 + ϒ

2He4 x 3 6C12

6C12 + 2He4 8O16 and then. . . . .

2 x 6C12 12Mg24

2 x 6C12 10Ne20 + 2He4

2 x 8O16 14Si28 + 2He4

2 x 8O16 16S22

16S32 + 2He4 18Ar36

18Ar36 + 2He4 20Ca40

20Ca40 + 2He4 22Ti44

22Ti44 + 2He4 24Cr48

24Cr48 + 2He4 26Fe52

• For H to fuse into He, it took about 7 million years

• For He into C and O – about 500 000 years• For C and O to go through the fusion process

and form Ne and Mg, only about 600 years• Ne and O formed into Si and S in about 6

months• And Si into Fe, where the process stops – only

about one day was needed• It stops with Fe because it is very stable

So, where did everything come from?

• The elements formed, and as they did, the heavier ones bonded and exerted a gravitational force pulling others into themselves

• Planets formed, but more important, stars were born

• H and He coalesced into concentrated areas of gas – and with gravity – stars formed

Star elements.

• H and He joined and started the fusion process to form nebulas– As the gravity these elements exerted pulled

inwards, the velocity of the atoms and the internal temperature increased immensely

– With a higher density, more collisions occurred– This created a plasma center and a fusion energy

source that gives off high levels of energy– Fusion is an exothermic rxn – (gives off energy)

Nucleosynthesis in sum:

The Life Cycle of a Star• The life cycle of a star is determined by its

mass – more mass, shorter life cycle• The original matter coalesces into a Nebula• Over time, the H gas in the nebula pulls

together and its gravity makes it spin• As the temperature approaches 15 000 000 000 degrees, fusion begins and a sun is started

The Crab Nebula

Orion Nebula

Rosette Nebula

Eagle Nebula

Helix Nebula

Menkhib-California Nebula

Seagull Nebula

Wizard Nebula

Starburst

Space Dust

Young Stars

Planetary Collisions Add Even More Elements into the Universe

• The H becomes He through fusion, releases massive amounts of energy in the process

• As the H runs out, the star cools and becomes a Red Giant– Eventually, the He goes through the fusion process

and becomes carbon causing the gravity to increase its pull inwards

• As the core collapses, a White Dwarf is formed

• The tug-of-war between gravity and fusion causes the star to go Supernova

Nucleosynthesis in a Star

Gravitational Collapse

Supernova Stars

The Star’s End is Near. . . . . • As the fusion process continues towards Fe, its instability increases

– When the core is Fe, fusion stops and since more energy is used than released, in less than a second, there is a gravitational collapse of the star

– The core temp reaches 100 000 000 000 degrees or more, and the repulsive force of the nuclei overcome the force of gravity

– The star explodes – showering the universe with its elements

– As the elements fly out, many are fused into newer, heavier elements and isotopes, as well as radiation

• After the Supernova explodes, the remnants become a Neutron Star with massive density and gravitational force

• Soon, the Neutron Star will swallow itself and become a Black Hole

Neutron Star Cross Section:

Dark Matter to Matter?

The Early Periodic Table

Although alchemists classified elements for centuries according to their own schemes, it was not until 1789 that the first real scientific listing of the elements was made.

Antoine Lavoisier listed elements that could not be further broken down in his book on Chemistry.

• Whereas he correctly listed some elements, he mistakenly listed light and caloric (heat) as elements also

• Johannes Dobereiner (1780-1849)– He grouped elements based on similarities– He also noticed a trend when he did this• For example:Ca (40); Sr (88) and then Ba (137) would be grouped

togetherHowever: Sr is the average of the two elements around it!(40 + 137) / 2 = 88This was also noted for other groups like Cl, Br and I;

and Li, Na and K

• In 1829, Dobereiner set up what he called the Law of Triads– As more and more elements were found, and

more accurate information attained about them, the Law of Triads fell to the wayside

Alexandre Bequeyer de Chancourtois (1820-86)

• de Chancourtois listed the elements according to their atomic weight

• The unique thing was that he wrapped the information around a cylinder – more of a periodic pole than table

John Newlands (1837-98)

• By the time Newlands worked, there were 62 known elements

• He also grouped them according to their atomic weight– He noted that after 8 elements, there were similar

properties• In 1863, he called these groupings the Law of

Octaves– This too was discarded as more knowledge was

gained

August Kekule (1858) andJulius Lothar Meyer (1870)

• Both scientists grouped the known elements (49 at the time) into groups based on valency– This is the outermost orbit of electrons and how

many electrons are in that orbit

Dmitri Mendeleev (1834-1907) is given usually given credit for developing the first periodic table based on atomic weight and properties – it allowed him to predict new elements.

His predictions were proven true with the discovery of gallium, scandium and germanium

However, it was Henry Moseley (1887-1915) who set it up using the atomic number (Z)

He used x-rays to note the frequency of the element as well as the number of p+

The chart became arranged according to atomic number rather than atomic weight

Glenn Seaborg (1912-1999)

• Seaborg bombarded U-238 with n0 and created the transuraniumelements, #94 through 102

• He created Neptunium and Plutonium in 1940– For this he would win the

Nobel Prize for Chemistry!!!!!• Eventually – element #106

would be named for him and his accomplishments in 1974

Today’s Periodic Chart• As of today – we have 118 elements• 94 of these occur naturally on Earth –

although we are discovering some of the others in very small trace amounts

• #43, 61 and those above #83 have no stable isotopes

• Francium - #87 was the last natural element found (1939)

Some Elemental Trivia. . . . . .• Element 117, ununseptium, is the newest

element– 6 atoms were made in Russia in April 2010– Official names will be chosen later by an

international committee• #118, ununoctium, was made in 2008• The rarest elements are Protactium (#91) and

Astatine (#85) with only about 1 oz existing on Earth!

• The most expensive element is Rhodium at $2500 per ounce (used in jewelry and airplane sparkplugs); followed by Platinum ($1544/oz); Gold ($1243/oz) and Iridium ($750/oz)

• Tellurium has the longest radioactivity – a half-life of 8 x 1024 years

• Beryllium is the shortest at 2.7 x 10-21 seconds• The most common element is, of course,

hydrogen which makes up 72% of the universe• Only Hg and Br are naturally liquids –

everything else are gases or solids

There are 10 Elements have symbols that don’t match their names!

Symbol Name Original NameSb Antimony StibiumAu Gold AuriumFe Iron FerrumPb Lead PlumbiumHg Mercury HydrargyriumK Potassium Kalim (Potash)Ag SilverArgentumNa Sodium NatriumSn Tin StannumW Tungsten Wolfram

Of course, there are other forms of the Periodic Chart. . . . .

Next Up• Next up is a closer examination

of the Periodic Chart and its components

• The Periodic Trends and Elemental Groups and Periods

• Be prepared to learn and study!