Chemistry Chapter 4: Chemistry Chapter 4: The Periodic TableThe Periodic Table

Section 4: FromWhere Did the Section 4: FromWhere Did the Elements Come?Elements Come?

Key TermsKey Terms Nuclear reactionNuclear reaction – reaction that – reaction that

affects atomic nucleusaffects atomic nucleus Superheavy elementSuperheavy element – an – an

element with an atomic # > 106element with an atomic # > 106 TransmutationTransmutation – changing from – changing from

one element to anotherone element to another

Key Terms 2Key Terms 2

E=mcE=mc22 – Enstein’s quantitative – Enstein’s quantitative description of the mass energy-description of the mass energy-relationshiprelationship

Here e, m and c are energy, mass Here e, m and c are energy, mass & the speed of light, respectively.& the speed of light, respectively.

Key Terms 3Key Terms 3

SupernovaSupernova – explosion of stars more – explosion of stars more than 100x more massive than the sunthan 100x more massive than the sun

The blast is caused by conversion of The blast is caused by conversion of core H & He into elements up to Fe.core H & He into elements up to Fe.

During the explosion, this change During the explosion, this change yields collapse & formation of ele-yields collapse & formation of ele-ments with higher atomic # than Fe.ments with higher atomic # than Fe.

Key Terms 4Key Terms 4

Synthetic elementsSynthetic elements – created by – created by chemists using chemists using particle acceleratorsparticle accelerators, , these elements do not occur naturally these elements do not occur naturally and have atomic # > 92.and have atomic # > 92.

Cyclotron Cyclotron – charged particle acceler-– charged particle acceler-ator 1ator 1stst invented by the American sci- invented by the American sci-entist E.O. Lawrence in 1930entist E.O. Lawrence in 1930

Key Terms 5Key Terms 5

SynchrotronSynchrotron – used to create – used to create superheavy elementssuperheavy elements

This device accelerates a few types of This device accelerates a few types of charged particles past 1/10charged particles past 1/10thth the speed the speed of light, c.of light, c.

One tenth c is the top speed that One tenth c is the top speed that cyclotronscyclotrons can yield. can yield.

Things To Know/AnswerThings To Know/Answer

How do the naturally occurring How do the naturally occurring elements form?elements form?

How does a transmutation change How does a transmutation change one element into another?one element into another?

How are particle accelerators used How are particle accelerators used to create synthetic elements?to create synthetic elements?

Natural ElementsNatural Elements Only 93 of the elements in the Only 93 of the elements in the

periodic table are found in nature.periodic table are found in nature. Technetium,Tc; promethium, Pm, Technetium,Tc; promethium, Pm,

& neptunium, Np, are found in & neptunium, Np, are found in the spectra of stars.the spectra of stars.

C, H, O, N, P & S are most of the C, H, O, N, P & S are most of the atoms in living things.atoms in living things.

Natural ElementsNatural Elements 2 2

Popular theory – common and natural Popular theory – common and natural elements were created in the centers elements were created in the centers of stars billions of years ago, shortly of stars billions of years ago, shortly after the “Big Bang”after the “Big Bang”

H & He formed after the Big Bang H & He formed after the Big Bang through cooling of temperatures.through cooling of temperatures.

Natural Elements 3Natural Elements 3

Here, energy was able to become Here, energy was able to become subatomic particles. subatomic particles.

These formed H & He in clouds that These formed H & He in clouds that gravity centralized.gravity centralized.

The cloud gathering yielded great The cloud gathering yielded great solar density which caused rising solar density which caused rising central temperature & pressure.central temperature & pressure.

Natural Elements 4Natural Elements 4

Nuclear reactions started in these Nuclear reactions started in these solar centers.solar centers.

Stars have fusion reactions where Stars have fusion reactions where 4H become 1He with an apparent 4H become 1He with an apparent loss of mass that becomes loss of mass that becomes energyenergy..

E=mcE=mc22 describes this change. describes this change.

Natural Elements 5Natural Elements 5

Other elements can form by Other elements can form by fusion. See Figure 28 on pg. 144.fusion. See Figure 28 on pg. 144.

See See www.scilinks.orgwww.scilinks.org Origin of Origin of Elements under code HW4093. Elements under code HW4093.

TransmutationsTransmutations

Middle Ages = alchemists trying Middle Ages = alchemists trying to turn Pb into Au via ordinary or to turn Pb into Au via ordinary or non nuclear chemical reactions.non nuclear chemical reactions.

Were they successful? See Were they successful? See Alchemy at code HW4006.Alchemy at code HW4006.

Transmutations 2Transmutations 2

Rutherford saw particle tracks in Rutherford saw particle tracks in his experiments.his experiments.

He reasoned that they came from He reasoned that they came from disintegration of atomic nuclei disintegration of atomic nuclei after being struck by after being struck by αα-particles.-particles.

Transmutations 3Transmutations 3

W.D. Harkins, an American, & W.D. Harkins, an American, & P.M.S. Blackett confirmed that Y P.M.S. Blackett confirmed that Y shaped tracks meant transmutationshaped tracks meant transmutation

This was b/c N disintegrated into O This was b/c N disintegrated into O and a proton when struck by an and a proton when struck by an αα--particle.particle.

Synthetic ElementsSynthetic Elements

Researchers hopped on the Researchers hopped on the transmuting train & synthesized transmuting train & synthesized elements that were not available elements that were not available in nature w/ in nature w/ particle accelerators.particle accelerators.

Cyclotrons Cyclotrons && Synchrotrons Synchrotrons use use successive pulses of energy to successive pulses of energy to speed up charged particles. speed up charged particles.

Synthetic Elements 2Synthetic Elements 2

They make particles collide at They make particles collide at high speed and energy, fuse, and high speed and energy, fuse, and form heavier elements.form heavier elements.

Greater speed yields greater mass Greater speed yields greater mass and more difficulty continuing and more difficulty continuing accelerationacceleration

Synthetic Elements 3Synthetic Elements 3

The charge particles must reach The charge particles must reach successive pulses on time.successive pulses on time.

If not, they slow down, lose energy If not, they slow down, lose energy and fail to fuse.and fail to fuse.

Most superheavy elements last for a Most superheavy elements last for a small fraction of a s except for 114.small fraction of a s except for 114.

Synthetic Elements 4Synthetic Elements 4

The only time scientists synthe-The only time scientists synthe-sized element 114, it lasted for sized element 114, it lasted for 30s then decayed to 112. Why is 30s then decayed to 112. Why is this problematic? this problematic?

Russian scientists bombarded Pu-Russian scientists bombarded Pu-214 with Ca-40 for 40 days to 214 with Ca-40 for 40 days to create 114.create 114.

Synthetic Elements 5Synthetic Elements 5

Many researchers view element Many researchers view element 114 as the beginning of a stable 114 as the beginning of a stable set of synthetic elements. Why?set of synthetic elements. Why?