Creation of the ElementsCreation of the Elements

Chapter 4Chapter 4

Section 4Section 4

http://www.astro.utoronto.ca/~mcclure/problems/problems.html

Hydrogen was formed from Hydrogen was formed from energy after the Big Bangenergy after the Big Bang

As the universe As the universe cooled, some of the cooled, some of the energy was converted energy was converted into protons, neutrons into protons, neutrons and electrons.and electrons.

These particles formed These particles formed the first atoms, mostly the first atoms, mostly H but also some He.H but also some He.

In this early process, In this early process, energy was converted energy was converted into matter according into matter according to the equationto the equationE = mcE = mc22

The hydrogen atoms began to The hydrogen atoms began to form starsform stars

Gravitational Gravitational attraction pulled attraction pulled the H atoms closer the H atoms closer and closer together.and closer together.

Clouds became Clouds became denser, pressures denser, pressures and temperatures and temperatures at the center of the at the center of the stars increased, and stars increased, and stars were born.stars were born.

http://homepages.wmich.edu/~korista/stargal-images/first_stargals.jpg

Elements 2-92 were created by Elements 2-92 were created by nuclear fusion nuclear fusion

The interior of stars is The interior of stars is very hot, giving the very hot, giving the energy required for energy required for nuclei to come close nuclei to come close enough together to enough together to undergo nuclear undergo nuclear fusion.fusion.

Mass is not conserved, Mass is not conserved, but is converted to but is converted to energy according to energy according to the equation E = mcthe equation E = mc22..

In the first phase, 4 In the first phase, 4 protons (protons (11H) can come H) can come together to form He.together to form He.

http://www.ichthus.info/BigBang/intro.html

Helium formed in fusion can undergo Helium formed in fusion can undergo further fusion reactions to form further fusion reactions to form

heavier elements.heavier elements.

These Elements are Released into These Elements are Released into SpaceSpace

The specific elements The specific elements formed in a star formed in a star depend ondepend on Temperature of starTemperature of star Mass of starMass of star Stage of DevelopmentStage of Development

Eventually the fuel is Eventually the fuel is used up, and often the used up, and often the star explodes, star explodes, releasing its elements releasing its elements into space to be used into space to be used in new stars or in new stars or planets.planets.

http://nexus.polaris.net/services/image-archive/space/interstellar/?D=A

Artificial elements are created Artificial elements are created by transmutationby transmutation

Elements 93-100 were Elements 93-100 were created by bombarding created by bombarding nuclei with charged nuclei with charged particles such as particles such as protons and alpha protons and alpha particles.particles.

These charged particles These charged particles can be accelerated by a can be accelerated by a cyclotron.cyclotron.

This picture shows a This picture shows a cyclotron at UC, cyclotron at UC, Berkeley in 1942.Berkeley in 1942.

http://www.flickr.com/photos/12567713@N00/124523846/

The First TransmutationThe First Transmutation

The first transmutation that The first transmutation that was identified was in 1919:was identified was in 1919:

1414N + N + 44He He 1717O + O + 11HH

Nitrogen was transformed Nitrogen was transformed into oxygeninto oxygen

Superheavy elements Superheavy elements

Higher-atomic-mass elements (greater Higher-atomic-mass elements (greater than atomic number 100) were created by than atomic number 100) were created by crashing nuclei into each other using crashing nuclei into each other using accelerators such as synchrotrons. accelerators such as synchrotrons.

1212C + C + 244244Cm Cm 254254No + 2No + 211nn carbon curium nobelium neutronscarbon curium nobelium neutrons

These elements are very unstable.These elements are very unstable.e.g. Only 3 atoms of element 109 were e.g. Only 3 atoms of element 109 were created and they existed for only 0.0034 created and they existed for only 0.0034 seconds.seconds.