Element Abundances

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1 Familiar ways of classifying the elements IA IIA IIIB IVB VB VIB VIIB VIIIB IB IIB IIIA IV A V A VIA VIIA Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb T e I Xe Y Rb Sr Hf T a W Re Os Ir Pt Au Hg Tl Pb Bi Po At Rn La Cs Ba B C N O F Ne Li Be  Al Si P S Cl  Ar Na Mg Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge  As Se Br Kr  Sc K Ca  Ac Fr Ra 3  4  5 6  7  8 9 10 11 12  13  14  15 16  17  18 19 20  21 22  23  24  25 26  27  28 29 30 31 32 33 34 35 36 37 38 39 40  41 42  43  44  45 46  47  48 49 50 51 52 53 54 55 56 57  72  73  74  75 76  77  78 79 80 81 82 83 84 85 86 87 88 89 VIIIA 58 59 60 61 62 63 64 65 66 67 68 69 70  71 90 91 92 93 94 95 96 97 98 99 100 101 102 103     p     e     r       i     o       d H 1 2 3 4 5 6 7 1  He 2 metals non-metals semi-conductors (semi-metals; metalloids) IA IIA IIIB IVB VB VIB VIIB VIIIB IB IIB IIIA IV A V A VIA VIIA VIIIA Zr Nb Mo T c Ru Rh Pd Ag Cd In Sn Sb T e I Xe Y Rb Sr Hf T a W Re Os Ir Pt Au Hg Tl Pb Bi Po At Rn Cs Ba B C N O F Ne Li Be  Al Si P S Cl  Ar Na Mg Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge  As Se Br Kr  Sc K Ca Fr Ra 3  4  5 6  7  8 9 10 11 12  13  14  15 16  17  18 19 20  21 22  23  24  25 26  27  2 8 29 30 31 32 33 34 35 36 37 38 39 40  41 42  43  44  4 5 46  47  48 49 50 51 52 53 54 55 56 57- 71  72  73  74  75 76  77  78 79 80 81 82  83  84 85 86 87 88 89- 103 He H 1 2 2 3 4 5 6 7 1 transition elements  Alternatively ... COSMIC ABUNDANCE of the ELEMENTS and NUCLEOSYNTHESIS February 3, 2005 

Transcript of Element Abundances

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Familiar ways of classifying the elements

IA

IIA

IIIB

IVB

VB

VIB

VIIB VIIIB IB IIB

IIIA

IVA

VA

VIA

VIIA

Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te I XeYRb Sr 

Hf  Ta W Re Os Ir Pt Au Hg Tl Pb Bi Po At RnLaCs Ba

B C N O F NeLi Be

 Al Si P S Cl  Ar Na Mg

Ti V Cr  Mn Fe Co Ni Cu Zn Ga Ge  As Se Br Kr  ScK Ca

 AcFr Ra

3   4   5 6   7   8 9 10

11 12   13   14   15 16   17   18

19 20   21 22   23   24   25 26   27   28 29 30 31 32 33 34 35 36

37 38 39 40   41 42   43   44   45 46   47   48 49 50 51 52 53 54

55 56 57   72   73   74   75 76   77   78 79 80 81 82 83 84 85 86

87 88 89

VIIIA

58 59 60 61 62 63 64 65 66 67 68 69 70   71

90 91 92 93 94 95 96 97 98 99 100 101 102 103    p    e    r      i    o      d

H

1

2

3

4

56

7

1  He

2

metals

non-metals

semi-conductors

(semi-metals; metalloids)

IA IIA

IIIB

IVB

VB

VIB

VIIB VIIIB IB IIB

IIIA

IVA

VA

VIA

VIIA

VIIIA

Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te I XeYRb Sr 

Hf  Ta W Re Os Ir Pt Au Hg Tl Pb Bi Po At RnCs Ba

B C N O F NeLi Be

 Al Si P S Cl  Ar Na Mg

Ti V Cr  Mn Fe Co Ni Cu Zn Ga Ge  As Se Br Kr  ScK Ca

Fr Ra

3   4   5 6   7   8 9 10

11 12   13   14   15 16   17   18

19 20   21 22   23   24   25 26   27   28 29 30 31 32 33 34 35 36

37 38 39 40   41 42   43   44   45 46   47   48 49 50 51 52 53 54

55 5657-71   72   73   74   75 76   77   78 79 80 81 82   83   84 85 86

87 8889-103

HeH1 2

2

3

4

5

6

7

1

transition elements

 Alternatively...

COSMIC ABUNDANCE of the ELEMENTS and NUCLEOSYNTHESIS February 3, 2005 

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Geochemical variations on the periodic table...

IA

IIA

IIIB

IVB

VB

VIB

VIIB VIIIB IB IIB

IIIA

IVA

VA

VIA

VIIA

Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te I XeYRb Sr 

Hf  Ta W Re Os Ir Pt Au Hg Tl Pb Bi Po At RnLaCs Ba

B C N O F NeLi Be

 Al Si P S Cl  Ar Na Mg

Ti V Cr  Mn Fe Co Ni Cu Zn Ga Ge  As Se Br Kr  ScK Ca

 AcFr Ra

3   4   5 6   7   8 9 10

11 12   13   14   15 16   17   18

19 20   21 22   23   24   25 26   27   28 29 30 31 32 33 34 35 36

37 38 39 40   41 42   43   44   45 46   47   48 49 50 51 52 53 54

55 56 57   72   73   74   75 76   77   78 79 80 81 82 83 84 85 86

87 88 89

VIIIA

58 59 60 61 62 63 64 65 66 67 68 69 70   71

90 91 92   93   94 95 96 97 98 99 100 101 102   103

H

1

2

3

4

5

6

7

1  He

2

 ABUNDANCE 

abundant in cosmos but not in(on) Earth

major elements in Earth (>1 wt%)~

trace elements (< 0.1%; some < 1 ppm)~

minor elements in Earth (0.1 < conc < 1%)~~

 Al13

Ga31

400 atoms

10 atoms6

Si14

Ge32

118 atoms

10 atoms6

relative abundances of chemicallysimilar elements

SIZES OF ATOMS (IONIC RADII)

SbSnIn

 AtPoTlHg

 As

OLi Be B C

Na Mg  Al Si

K Ca TiSc

Rb

Cs

Fr 

Sr 

Ba

Ra

Y

La

 Ac

Zr 

Hf 

Th

V

Ta

Pa

Nb

Cr 

Mo

W

U

Mn

Tc

Re

Fe Co

Os Ir Pt

RuRh Pd

NP

 Au

PbBiCd

 Ag

Ni GeGaZnCu

F

Cl

Br 

I

S

Se

Te

Ionic radius increases coming out of the figure.Sizes apply to the valence state that is mostcommon in natural systems.

"Host" mineral

(made of majorelements)

Trace elementssubstitute into suit-able lattice sites

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IA

IIA

IIIB

IVB

VB

VIB

VIIB VIIIB IB IIB

IIIA

IVA

VA

VIA

VIIA

Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te I XeYRb Sr 

Hf  Ta W Re Os Ir Pt Au Hg Tl Pb Bi Po At RnLaCs Ba

B C N O F NeLi Be

 Al Si P S Cl  Ar Na Mg

Ti V Cr  Mn Fe Co Ni Cu Zn Ga Ge  As Se Br Kr  ScK Ca

 AcFr Ra

3   4   5 6   7   8 9 10

11 12   13   14   15 16   17   18

19 20   21 22   23   24   25 26   27   28 29 30 31 32 33 34 35 36

37 38 39 40   41 42   43   44   45 46   47   48 49 50 51 52 53 54

55 56 57   72   73   74   75 76   77   78 79 80 81 82 83 84 85 86

87 88 89

VIIIA

58 59 60 61 62   63   64 65 66 67 68 69 70   71

90 91 92 93 94 95 96 97 98 99 100 101 102 103    p    e

    r      i    o      d

H

1

2

3

4

5

6

7

1  He

2

highly volatile (atmophile)

moderately volatile

refractory

siderophile

These geochemical tendencies largelydetermine where in the Earth many

elements are sequestered – e.g.,siderophile elements are concentratedin the core; volatile elements werepartially lost from the Earth during itshot early history.

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Some general features of cosmic abundance curve

  >75% of the mass of the universe is hydrogen>99% is H + He

(note: These statements do not  apply to the Earth)

  Elemental abundances drop off exponentially with increasing atomic number (Z)up to Z ~ 60; therafter remain ~constant

  Li, Be & B show marked depletion relative to both higher and lower-Z elements

  There is a pronounced abundance peak in the vicinity of Fe, as well as a few lessobvious peaks at higher Z

  Even-Z elements are more abundant than their odd-Z neighbors

A Z N no. of stable isotopes

odd odd even 50

odd even odd 55

even odd odd 4

even even even 165!

COSMIC ABUNDANCES   of the elements

atomic number, Z

10 20 30 40 50 60 70 80 90

H

He

Li

Be

B

C

Si Fe

Pb

Th

U   l  o  g

  r  e   l  a   t   i  v  e  a   b  u  n   d  a  n  c  e   (   S

   i   =   1   0

   )   6

   1   0 0

-2

2

4

6

8

10rare earth elements:

"odd-even" effect 

La

Lu

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   l  o  g  o   f  a

   b  u  n   d  a  n  c  e   (  r  e   l  a   t   i  v  e   t  o   1   0

   S   i   a   t  o  m  s   )

   6

Z

cosmic abundances of the elements(Anders & Ebihara, 1982)

even Zodd Z

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similarilty in composition of chondrites and solar atmosphere...

Note:  This diagram is a useful illustration, but bear in mind that:

1) it is a log-log plot ( and just about anything can appear to be linear on such a plot!)

2) the chondrites represented are actually metamorphic rocks, so their compositionmay not be "primitive" in all respects

O

MgFe

SNa  Al

CaNi

Cr 

MnP

CoK

Ti

ZnCu

GeScSr 

BRb

BaY

Pb

Li

CeLa

BePr 

ThTm

log relative abundance in C1 chondrites (Si = 10 )610

-2 0 2 4 6 8

   l  o  g

  r  e   l  a   t   i  v  e  a   b  u  n   d  a  n  c  e

   i  n  s  o   l  a  r  a   t  m  o  s  p   h  e  r  e

   (   S   i  =   1   0

   )

   1   0

   6

-2

0

2

4

6

8

*

* Chondrites are the most "primitive" of meteorites -- i.e., ones we believe representthe original, overall composition of the solar system. Five distinct types of chondritesare recognized.

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red numbers:  number of solar masses

green numbers:  time on main sequence

M   A     S  E  Q  U  

E    (  b 

r  n n  ) 

I  N  

E  N  C  

H    u i  g 

red 

giants

whitedwarfswhite

 w rfs

bluegiants

red dwarfs

SUN

22 Ma

68 Ma

232 Ma

1.6 Ga

9 Ga

9

5

3

1.5

4.4 4.2 4.0 3.8 3.6

0.1

1

10

100

1000

1E4

1E5

log surface temperature, K 

   l  u  m   i  n  o  s   i   t  y  r  e   l  a   t   i  v  e   t  o   S  u  n

Hertzsprung-Russell Diagram

He burning

"Burning" of hydrogen and helium in first-generation stars

First-generation stars are ones that have come together from an"original" hydrogen-helium cloud – that is, they do not represent "re-processed" stellar material from a previous supernova explosion (theSun is actually a second-generation star ). In first-generation stars,hydrogen "burning" to produce helium occurs by these reactions:

H11 H

11

+ H21 + energy

H21 H

11+ He

32 + energy

He32He

32

+ He42 H

11H

11

+ energy++

The elements as we know them are created in the interiors of stars...

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On the main sequence, helium is the main product of hydrogenburning. A gravitationally stable core of helium is produced in the star,and hydrogen burning continues on the surface of the core. As H-burning migrates outward, the luminosity of the star increases slightly:

If the star is massive enough to achieve the required temperature anddensity in the core, is initiated and heavier elementscan be synthesized

This process is exceedingly inefficient because is unstable and-16

decays with a half-life of only 10 s. What probably happens is thatanother helium nucleus is immediately absorbed to make a carbonnucleus:

or 

helium burning 

He42+He

42 Be

84

Be84

+Be84 He

42 C

126

+ He42 C

126He

42He

42

+

hydrogen burning 

Note:  These helium nuclei are actually positively-charged alphaparticles and repel each other strongly (remember Mr. Coulomb?).Extreme temperatures and pressures are required to get them tofuse: He burning can occur only in stars having masses of 80% ormore of our Sun. This "triple-alpha" process is the key tomaking heavier elements...

Hecore

H burning here

(endothermic!)

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He burning here

carboncore

carbon + someheavier elements

outer envelope super-heated; greatly expands

1 2   3   4

nuclear fuel exhausted; star collapses to white dwarf 

5

helium burning 

He burning sustains red giants

for a few 10s of Ma at most 

Somewhat heavier elements...

If a red giant is sufficiently massive, successively heavier elements can besynthesized by addition of alpha particles (He nuclei) to carbon...

56 56This "alpha-process" can continue up to Ni (which decays to Fe), butelements heavier than Fe cannot be made by this process because the

repulsion between large, positively-charged nuclei and  particles is too strong.

Note that the nuclei forming by this process are all even-Z. Smallerabundances of odd-Z nuclei are produced by reactions among the fusionproducts, such as:

+ He42C

126

16O8

16O

8

+ He4

2

20Ne

10etc.

+H

1

1C

12

6

23

Na11C

12

6 +

and16

O8+   31

P1516

O8 H11+

This creates further possibilities, e.g...

and

+ H11C

126

13N7 +  then

13N7

13C6

++

  +

16O8

+ +13C6 He

42

nThis type of reaction iscrucial because neutrons area product! (more soon)

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Later generations of stars and the CNO cycle

That's about as much as we need to know about first-generation stars. The

key thing to remember is that when these explode, they contribute elementsheavier than H and He to the interstellar gas, so the next generation of stars canbegin with a different, more "versatile" fuel. Subsequent stars can burn hydrogenin the CNO cycle, in which hydrogen nuclei are added to carbon to produce firstnitrogen and then oxygen. This mode of H burning requires less extremeconditions than the proton-proton fusion reactions on p. 6. The Sun is nowburning H in the CNO cycle:

+ H11C

126

13N7

13N7

decaysC

136

C136 + H

11

14N7

15O8

decays 15N7

14N7 + H

11

15O8

He42

+15N7 + H

11 C

126

4 12end result:  4 protons fused to make He; C "released" for future use

H-burningHe-burning

C-burning

Ne-burningO-burning

Si-burning

H-burningunburned H

He-burning

unburned He

H-burning

unburned H

process fuel products temperature (K)

H-burningHe-burningC-burningNe-burningO-burningSi-burning

HHeCNeO

Mg to S

HeC, OO, Ne, Na, Mg

O, Mg

Mg to S

elements near Fe

6E72E88E815E82E93E9

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Z

N

   N   =

    Z

  " n d

 o f  t  b

  i  l  i y

  b a 

 s a t  "

Synthesis of heavy nuclei by neutron capture:the  and in second-generation starss- r-processes

Elements heavier than Fe: NEUTRON CAPTURE 

If there is a source of neutrons, the following type of reaction can occur 

If a nucleus absorbs too many  neutrons, it will eventually become too neutron-rich to be stable and decay by beta decay. Through neutron-capture reactions, itis possible to work up through most of the periodic table.

We recognize two distinct types of neutron-capture processes, which differ interms of the neutron flux required:

s-process:  moderate neutron fluxes in the late red-giant stage

r-process:  very high neutron fluxes in supernovae

 A A+1 X + neutron =  X z z 

neutronnucleus new, heavier 

nucleus

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Cd48

In49

Sn50

Sb51

62 63 64 65 66 67 68 69

70 71 72

73 74

s-process path

r-process

stableunstable tobeta decayN

Z

Creating heavy elements by neutron capture: An example...

Fe + n  (stable)56

Fe57

Fe + n  (stable)57

Fe58

Fe + n  (t = 45 d)58

Fe59

½

The way things proceed from here depends upon the neutron flux (no. of

neutrons available). , the next step would be:If the flux is limited 

Fe59 Co + e + 59

Co + n  (t = 5 y)59

Co60

½

Co60 Ni + e + Ni is stable)60 60

However, (lots of neutrons available), we can get59 59

past Fe: instead of decaying to Co, it absorbs another neutron...if the neutron flux is large

Fe + n  (t = 3E5 y)59 Fe60 ½

Fe + n  (t = 6 m)60

Fe61

½

Co61 Ni + e + Ni is stable)61 61

Fe61 Co + e + (t =1.65 h)61

½

So...We got to adifferent placebecause wehad moreneutronsavailable

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N

Z

Fe

Co

Ni

Cu

Zn

Ga

56 57 58 59 60 61 62 63 64 65 66 67 68

68 69 70 71

71 72 73

63 64 65 66

60 61 62 63 64 65

70

69

59 60

64 65 66 67 68 69

r-process

s-process

n capture

  decay

  decay

Z

N

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SUMMARY 

neutron capture

stellar fusion

spallation

Big Bang

atomic number 

   r   e   l   a   t   i  v   e    a

   b  u   n   d   a   n   c   e

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Neutron Activation:  “artificial” nucleosynthesis

 An example of neutron capture followed by beta decay (as in the s-process)...

Neutron activation is an analytical technique used extensively in the bio-,geo- and materials sciences for measurement of trace concentrations (e.g.1-100 ppm) of elements in a wide variety of materials. As the name suggests,it involves the use of a neutron flux in a research reactor to “activate” theelement of interest. This really means that the element (nucleus) of interestis “transmuted” -- by absorbing a neutron -- into a heavier nucleus that isradioactive. This “activated” nucleus is then detected by recording thegamma ray emitted when it disintegrates by beta decay.

  The sequence just described (neutron absorption followed by beta-decay)is analogous to a step along the s-process path (see class hand-out). Theonly difference in the case of neutron activation is that the source of neutrons

is a man-made reactor (and the target nuclei are different).

  Here’s an example: Analysis of SiO glass for sodium impurities...2

mostly SiO with2

a few Na atomsneutrons

23 24 23 24Na is “activated” by conversion to Na: Na + N Na

24  ( Na is radioactive)

Step 1 Place glass sample in reactor 

24Step 2 Detect Na decay events by counting    rays produced by the reaction 

glass sample

  detector 

24 - 24Na ( , ) Mg

11

12

23 24

Z Na11

23Na11

24

Mg12

24

23“activation” of Na by neutron absorption

-decay(t = 15h)1/2

On the familiar Z-N diagram...