chapter 4 section 4. natural and synthetic elements 93 naturally occurring elements 93 naturally...

Chapter 4Chapter 4

Section 4Section 4

Natural and Synthetic Natural and Synthetic ElementsElements

93 naturally occurring elements93 naturally occurring elements

Are they all found on Earth?Are they all found on Earth?– No, technetium, promethium, and No, technetium, promethium, and

neptunium are detected in the spectra of neptunium are detected in the spectra of starsstars

How do we get the rest of our elements?How do we get the rest of our elements?– They are synthetic or created in a labThey are synthetic or created in a lab

Naturally Occurring Naturally Occurring ElementsElements

The Big Bang TheoryThe Big Bang Theory– The universe “exploded”The universe “exploded”– After this the temperatures were in the After this the temperatures were in the

millions of Kelvinsmillions of Kelvins– Only energy could exist not matterOnly energy could exist not matter– As it expanded it cooled As it expanded it cooled – When it cooled the energy was When it cooled the energy was

converted to matter in the form of converted to matter in the form of electrons, protons, and neutronselectrons, protons, and neutrons


Big Bang TheoryBig Bang Theory– As the universe continued to cool the As the universe continued to cool the

first atoms formed – mostly hydrogenfirst atoms formed – mostly hydrogen– Over time gravitational attraction pulled Over time gravitational attraction pulled

the clumps of hydrogen together the clumps of hydrogen together – The clouds became denser, pressure The clouds became denser, pressure

increased, and temperature increased. increased, and temperature increased. This created starsThis created stars


What takes place in the center of What takes place in the center of stars?stars?– Nuclear reactionsNuclear reactions

Nuclear reaction:Nuclear reaction:– Reaction that involves a change in the Reaction that involves a change in the

composition of the nucleus of an atomcomposition of the nucleus of an atom– Ex: Hydrogen nuclei fused with one Ex: Hydrogen nuclei fused with one

another to form helium nucleianother to form helium nuclei


Nuclear Fusion:Nuclear Fusion:– Takes place under extreme heatTakes place under extreme heat– Kinetic energy of the nuclei is great Kinetic energy of the nuclei is great

enough to overcome the repulsion enough to overcome the repulsion between the protonsbetween the protons

Figure 4-31 Figure 4-31 – The mass lost is converted into energyThe mass lost is converted into energy


Hydrogen is being used = star Hydrogen is being used = star shrinking and temperature increasingshrinking and temperature increasing

As temp increases the helium fuse As temp increases the helium fuse with another to form elements of with another to form elements of higher atomic numbershigher atomic numbers

As the temp increases more elements As the temp increases more elements of even higher atomic #’s are createdof even higher atomic #’s are created

Figure 4-32Figure 4-32


What are the most massive atoms What are the most massive atoms that can be created this way?that can be created this way?– Iron and NickelIron and Nickel

When all of the hydrogen and helium When all of the hydrogen and helium are used up the star collapses and are used up the star collapses and then expands as a red giantthen expands as a red giant


When the red giant forms free When the red giant forms free protons and neutrons are producedprotons and neutrons are produced– They are absorbed by the nuclei of other They are absorbed by the nuclei of other

atoms creating elements with higher atoms creating elements with higher atomic numbersatomic numbers

– The red giant expels some of its matter The red giant expels some of its matter into space as well as the elements it into space as well as the elements it producedproduced


If the star is larger than the sun it If the star is larger than the sun it eventually explodes into a supernovaeventually explodes into a supernova

All of the elements are spread across All of the elements are spread across spacespace

Some of the exploded matter is Some of the exploded matter is eventually condensed into a new stareventually condensed into a new star


The new stars are mostly hydrogen but The new stars are mostly hydrogen but will still contain the heavier elements toowill still contain the heavier elements too

This creates a third generation starThis creates a third generation star

The sun is a fourth or fifth generation starThe sun is a fourth or fifth generation star

When the sun first formed it contained all When the sun first formed it contained all the naturally occurring elementsthe naturally occurring elements

Artificial ElementsArtificial Elements

Transmutation:Transmutation:– Changing 1 nucleus into another by Changing 1 nucleus into another by

radioactive disintegration or radioactive disintegration or bombardment with other particles bombardment with other particles

– High-speed alpha particles passing High-speed alpha particles passing through water vapor in a cloud chamberthrough water vapor in a cloud chamber Noted long thin tracks which were caused by Noted long thin tracks which were caused by

protonsprotons Same tracks were found when alpha Same tracks were found when alpha

particles passed through airparticles passed through air

Artificial ElementsArtificial Elements

This process helped scientists This process helped scientists discover that atomic nuclei in the air discover that atomic nuclei in the air were disintegrating when struck by were disintegrating when struck by helium nuclei into hydrogen nuclei helium nuclei into hydrogen nuclei plus the nuclei of another atomplus the nuclei of another atom

They found that transmutations They found that transmutations occurred by bombarding various occurred by bombarding various elements with alpha particleselements with alpha particles

CyclotronCyclotron Invented in 1930Invented in 1930

Charged particles are given successive pulses of Charged particles are given successive pulses of energyenergy

They are accelerated to very high energiesThey are accelerated to very high energies

The energetic ions are then made to collide with The energetic ions are then made to collide with atomic nucleiatomic nuclei

The accelerated ions fuse with the target nuclei The accelerated ions fuse with the target nuclei to produce a higher atomic numberto produce a higher atomic number

ProblemsProblems

There is a limit to the energies attained There is a limit to the energies attained by a cyclotronby a cyclotron

The problem was that the particle’s The problem was that the particle’s energy had to be balanced by an energy had to be balanced by an increase in massincrease in mass

Due to the increased mass the Due to the increased mass the particle’s accelerated more slowly particle’s accelerated more slowly causing it to arrive to latecausing it to arrive to late

SynchrotronSynchrotron

A synchrotron times the impulses to A synchrotron times the impulses to match the particle accelerationmatch the particle acceleration

Downfall:Downfall:– Can accelerate fewer types of particles Can accelerate fewer types of particles

than a cyclotronthan a cyclotron

Bonus:Bonus:– Enormous energies can be attainedEnormous energies can be attained

SynchrotronSynchrotron

Once they are accelerated they Once they are accelerated they collide head on with each othercollide head on with each other

Figure 4-34Figure 4-34

Superheavy elements can be createdSuperheavy elements can be created

TodayToday

Scientists are trying to create superheavy Scientists are trying to create superheavy elements that are more stable than those elements that are more stable than those prepared so farprepared so far

They think there is an “island of stability” in They think there is an “island of stability” in the region of atomic number 114the region of atomic number 114

Right now they exist for only a short Right now they exist for only a short amount of time and identification is very amount of time and identification is very difficultdifficult

chapter 4 section 4. natural and synthetic elements 93 naturally occurring elements 93 naturally...

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