DNA molecule

EXAMPLE: CARBON AND ITS ISOTOPES

CHEMICAL ELEMENTS & ISOTOPES

CARBON = C(COAL, DIAMOND)

C-226P+16NT½=9ms

M=22.056

C-96P+3N

T½=127msM=9.031

C-116P+5N

T½=20minM=11.0114

C-146P+8N

T½=5715y (from N-14 + n) (~4kBq in 70kg man, none in coal)

M=14.0032

C-186P+12N

T½=0.09sM=18.0268

C-126P+6N

STABLE – 18% ofbody mass

M=12.000000

C-126P+6N

STABLE – 18% ofbody mass

M=12.000000

C-136P+7N

STABLE – 1.1% of CM=13.0034

C-156P+9N

T½=2.45sM=15.0106

Question :

Where does nuclear energycome from ?

Clue :

E = mc2

Answer :

The slight excess of massof the less stable isotopes

is converted to energywhen isotopes are

converted from less stableto more stable ones.

CARBON ISOTOPES8 9 10 11 12 13 14 15 16 17 18 19 20 21 22

BORON ISOTOPES

NITROGEN ISOTOPES

CARBON ISOTOPESBORON

NITROGENCARBON

OXYGEN

BERYLLIUM BORON

NITROGENCARBON

OXYGEN

BERYLLIUMLITHIUMHELIUMHYDROGENneutron

FLUORINENEON

BORON

NITROGENCARBON

OXYGEN

BERYLLIUMLITHIUMHELIUMHYDROGENneutron

FLUORINENEON

SODIUMMAGNESIUMALUMINIUM

SILICONPHOSPHORUS

SULFURCHLORINE

ARGONPOTASSIUM

CALCIUM ALSO CALLED “CHART OF THE NUCLIDES”TABLE OF ISOTOPES

CARBON - 12

HHe

LiBe

BC

FO

N

SiAl

MgNa

Ne

ClS

P

Ar

CaK

ALSO CALLED “CHART OF THE NUCLIDES”TABLE OF ISOTOPES

Mg-35 (T½=0.07 sec)

Na-35 (T½=1.5 msec)

Al-35 (T½=0.03 sec)

Si-35 (T½=0.9 sec)

P-35 (T½=47 sec)

S-35 (T½=87.2 d)

Cl-35 (stable)Question :What is more radioactive ?A) an isotope with a long

half-life ?or

B) an isotope with a shorthalf-life ?

(assume you have 1 kg of each)

Clue # 1:Think of nuclear radiation

as a form of light(high energy form of light)

Clue # 2:Think of radioactive

isotopes as a store of energy(like an electric battery)

0 1 2 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

1

2

3

6

5

4

10

9

8

7

15

14

13

12

11

19

18

17

16

20

Clue # 3Little radiation for weeks

Powerful radiation for….….one minute ?

Identical car batteries – both charged to full

Answer :

The isotope with a shorthalf-life is more radioactive

because all its energy isradiated away quickly !!

CHART OF THE NUCLIDES – EXCESS MASSCHEMICAL ELEMENTS & ISOTOPES

RADIOACTIVE DECAY

“VALLEYOF

STABILITY”

Na-35(T½=1.5 msec)

Cl-35(stable)

Skipnext

HHe

LiBe

BC

FO

N

SiAl

MgNa

Ne

ClS

P

Ar

CaK

0 1 2 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

1

2

3

6

5

4

10

9

8

7

15

14

13

12

11

19

18

17

16

20 ALSO CALLED “CHART OF THE NUCLIDES”TABLE OF ISOTOPES

URANIUM-235 ( U-235 )

comprises 0.71% of

natural uranium (99.28% U-238) (0.006% U-234)

Example : U-235 + n° Y-96 + I-138 + 2n° (Uranium 235) (Yittrium 96) (Iodine 138)

C-12

IRON-56( Fe-56 )

Ba-138 (stable)

Cs-138 (T½=32.2 min)

Xe-138 (T½=14.1 min)

I-138 (T½=6.5 sec)

Mo-96 (stable)

Nb-96 (T½=23.4 hr)

Zr-96 (T½=2x1019 y)

Y-96 (T½=6.2 sec)

CHART OF THE NUCLIDES – EXCESS MASSTABLE OF ISOTOPES IN 3-D

U-235

U-235 + n° Y-96 + I-138 + 2n° (Uranium 235) (Yittrium 96) (Iodine 138)

I-138 (T½=6.5 sec)

Y-96 (T½=6.2 sec)Mo-96 (stable)

Ba-138 (stable)