This document discusses isotopes and nuclear reactions. It defines isotopes as atoms of the same element with different numbers of neutrons. It also describes how atomic mass is calculated based on isotope abundances. The document then discusses four types of nuclear reactions: fusion, fission, alpha decay, and beta decay. It provides examples of writing balanced nuclear equations and calculating half-life. Artificial transmutation and uses of nuclear technology like reactors and weapons are also summarized.
Postsecondary lesson for pre-u students or form 6th students on mole concept, stoichiometry, limiting reagent, spectrometry and percent yield and percent purity.
ADVANTAGES Nuclear power generation does emit relatively low amounts of carbon dioxide (CO2). The emissions of green house gases and therefore the contribution of nuclear power plants to global warming is therefore relatively little. This technology is readily available, it does not have to be developed first. It is possible to generate a high amount of electrical energy in one single plant
THE IMPORTANCE OF MARTIAN ATMOSPHERE SAMPLE RETURN.Sérgio Sacani
The return of a sample of near-surface atmosphere from Mars would facilitate answers to several first-order science questions surrounding the formation and evolution of the planet. One of the important aspects of terrestrial planet formation in general is the role that primary atmospheres played in influencing the chemistry and structure of the planets and their antecedents. Studies of the martian atmosphere can be used to investigate the role of a primary atmosphere in its history. Atmosphere samples would also inform our understanding of the near-surface chemistry of the planet, and ultimately the prospects for life. High-precision isotopic analyses of constituent gases are needed to address these questions, requiring that the analyses are made on returned samples rather than in situ.
Richard's entangled aventures in wonderlandRichard Gill
Since the loophole-free Bell experiments of 2020 and the Nobel prizes in physics of 2022, critics of Bell's work have retreated to the fortress of super-determinism. Now, super-determinism is a derogatory word - it just means "determinism". Palmer, Hance and Hossenfelder argue that quantum mechanics and determinism are not incompatible, using a sophisticated mathematical construction based on a subtle thinning of allowed states and measurements in quantum mechanics, such that what is left appears to make Bell's argument fail, without altering the empirical predictions of quantum mechanics. I think however that it is a smoke screen, and the slogan "lost in math" comes to my mind. I will discuss some other recent disproofs of Bell's theorem using the language of causality based on causal graphs. Causal thinking is also central to law and justice. I will mention surprising connections to my work on serial killer nurse cases, in particular the Dutch case of Lucia de Berk and the current UK case of Lucy Letby.
Richard's aventures in two entangled wonderlandsRichard Gill
Since the loophole-free Bell experiments of 2020 and the Nobel prizes in physics of 2022, critics of Bell's work have retreated to the fortress of super-determinism. Now, super-determinism is a derogatory word - it just means "determinism". Palmer, Hance and Hossenfelder argue that quantum mechanics and determinism are not incompatible, using a sophisticated mathematical construction based on a subtle thinning of allowed states and measurements in quantum mechanics, such that what is left appears to make Bell's argument fail, without altering the empirical predictions of quantum mechanics. I think however that it is a smoke screen, and the slogan "lost in math" comes to my mind. I will discuss some other recent disproofs of Bell's theorem using the language of causality based on causal graphs. Causal thinking is also central to law and justice. I will mention surprising connections to my work on serial killer nurse cases, in particular the Dutch case of Lucia de Berk and the current UK case of Lucy Letby.
Introduction:
RNA interference (RNAi) or Post-Transcriptional Gene Silencing (PTGS) is an important biological process for modulating eukaryotic gene expression.
It is highly conserved process of posttranscriptional gene silencing by which double stranded RNA (dsRNA) causes sequence-specific degradation of mRNA sequences.
dsRNA-induced gene silencing (RNAi) is reported in a wide range of eukaryotes ranging from worms, insects, mammals and plants.
This process mediates resistance to both endogenous parasitic and exogenous pathogenic nucleic acids, and regulates the expression of protein-coding genes.
What are small ncRNAs?
micro RNA (miRNA)
short interfering RNA (siRNA)
Properties of small non-coding RNA:
Involved in silencing mRNA transcripts.
Called “small” because they are usually only about 21-24 nucleotides long.
Synthesized by first cutting up longer precursor sequences (like the 61nt one that Lee discovered).
Silence an mRNA by base pairing with some sequence on the mRNA.
Discovery of siRNA?
The first small RNA:
In 1993 Rosalind Lee (Victor Ambros lab) was studying a non- coding gene in C. elegans, lin-4, that was involved in silencing of another gene, lin-14, at the appropriate time in the
development of the worm C. elegans.
Two small transcripts of lin-4 (22nt and 61nt) were found to be complementary to a sequence in the 3' UTR of lin-14.
Because lin-4 encoded no protein, she deduced that it must be these transcripts that are causing the silencing by RNA-RNA interactions.
Types of RNAi ( non coding RNA)
MiRNA
Length (23-25 nt)
Trans acting
Binds with target MRNA in mismatch
Translation inhibition
Si RNA
Length 21 nt.
Cis acting
Bind with target Mrna in perfect complementary sequence
Piwi-RNA
Length ; 25 to 36 nt.
Expressed in Germ Cells
Regulates trnasposomes activity
MECHANISM OF RNAI:
First the double-stranded RNA teams up with a protein complex named Dicer, which cuts the long RNA into short pieces.
Then another protein complex called RISC (RNA-induced silencing complex) discards one of the two RNA strands.
The RISC-docked, single-stranded RNA then pairs with the homologous mRNA and destroys it.
THE RISC COMPLEX:
RISC is large(>500kD) RNA multi- protein Binding complex which triggers MRNA degradation in response to MRNA
Unwinding of double stranded Si RNA by ATP independent Helicase
Active component of RISC is Ago proteins( ENDONUCLEASE) which cleave target MRNA.
DICER: endonuclease (RNase Family III)
Argonaute: Central Component of the RNA-Induced Silencing Complex (RISC)
One strand of the dsRNA produced by Dicer is retained in the RISC complex in association with Argonaute
ARGONAUTE PROTEIN :
1.PAZ(PIWI/Argonaute/ Zwille)- Recognition of target MRNA
2.PIWI (p-element induced wimpy Testis)- breaks Phosphodiester bond of mRNA.)RNAse H activity.
MiRNA:
The Double-stranded RNAs are naturally produced in eukaryotic cells during development, and they have a key role in regulating gene expression .
3. Isotopes
Isotopes: Atoms with the same number of protons,
but different numbers of neutrons.
Isotopes are atoms of the same element (same
atomic number) with different mass numbers
Isotopes of chlorine
35
Cl 37
Cl
17 17
chlorine 35 chlorine 37
5. Isotopes
Atomic mass
-Listed on the periodic table
-Gives the mass of “average” atom of each element
compared to 12
C
-Average atomic mass based on all the isotopes and
their abundance %
-Atomic mass is not a whole number…it’s a weighted
average
Na
22.99
6. Isotopes
Atomic mass calculations:
Gallium is a metallic element found in small lasers
used in compact disc players. In a sample of
gallium, there is 60.2% of gallium-69 (68.9 u) atoms
and 39.8% of gallium-71 (70.9 u) atoms. What is
the atomic mass of gallium?
Mass1 x Abundance1 + Mass2 x Abundance2 = Average atomic mass
69.7u = Average atomic mass
68.9u x 60.2% + 70.9u x 39.8% = Average atomic mass
7. Isotopes
Atomic mass calculations analogy:
A chemistry student’s grade is weighted. Tests
are worth 50.%, labs are 25%, and homework is
worth 25%. A student's test average is 85.0%, lab
average is 77.0%, and homework is 91.0%.
What is the student’s average?
8. Isotopes
Atomic mass calculations:
A sample of boron consists of 10
B (mass 10.0 u) and
11
B (mass 11.0 u). If the average atomic mass of B
is 10.8 u, what is the % abundance of each boron
isotope?
9. Isotopes
A sample of boron consists of 10
B (mass 10.0 u) and 11
B (mass 11.0 u). If the average
atomic mass of B is 10.8 u, what is the % abundance of each boron isotope?
Assign X and Y values:
X = % 10
B Y = % 11
B
Determine Y in terms of X
X + Y = 1 therefore Y = 1 - X
Solve for X:
X (10.0) + (1 - X )(11.0) = 10.8
10.0X + 11.0 – 11.0X = 10.8
10.0X – 11.0X = 10.8 –11.0
- 1.0X = - 0.2
X = 0.2
X = 20%
Y = 80%
.: the % abundances of 10
B and 11
B are 20% and 80%, respectively
11. NUCLEAR REACTIONS
2
H + 3
H 4
He + 1
n1 1 2 0
nuclear fusion - joining smaller
nuclei together to form larger nuclei
produces a lot of energy
Stars produce heavier atoms from the
fusion of many hydrogen atoms.
12. NUCLEAR REACTIONS
235
U + 1
n 139
Ba + 94
Kr + 3 1
n
235
U + 1
n 146
La + 87
Br + 2 1
n
235
U + 1
n 144
Cs + 90
Rb + 2 1
n
Nuclear fission
-large nuclei are broken in to smaller
nuclei by bombardment with a low
energy neutron
-often triggers a chain reaction of
events
-large amounts of energy
released
-Also known as radioactive
decay
92
92
92
0
0
0
0
0
0
56
57
55
36
35
37
13. NUCLEAR REACTIONS
Radioactive decay
(4 types)
– alpha decay: emitting an alpha
particle (a helium nucleus)
α particle = 4
2He
– beta decay: emitting an
electron (an electron particle
from the nucleus)
β particle = 0
-1e
– gamma decay: emitting
electromagnetic radiation
Ϫ particle = 0
0 Ϫ
(another type is emitting a
14. NUCLEAR REACTIONS
Property Alpha (α) Beta (β) Gamma (Ϫ) neutron (n)
nature of
radiation
4
2
He
nucleus
0
-1
e
electron
high
energy
radiation
1
0
n
charge 2+ 1- 0 0
mass 4 u 0 0 1 u
penetrating
ability
stopped by 4
cm of air or a
sheet of paper
stopped by 12
cm of air or
several mm of
paper
intensity
decreases by
10% by 3 cm
of lead
19. NUCLEAR REACTIONS
Balancing Nuclear Reactions
The sums of the atomic numbers on both sides of
the equation must be equal (92 = 90 + 2)
The sums of the mass numbers on both sides of an
equation must be equal (238 = 234 + 4)
238
92U → 234
90Th + 4
2He
20. NUCLEAR REACTIONS
Write an equation for the emission of an alpha
particle from 226
88Ra
226
88Ra → 4
2He + 222
86 ___Rn
22. Bi
Write an equation for the emission of a
beta particle from 214
82Pb
214
82Pb → 0
-1 e + 214
83 ___
NUCLEAR REACTIONS
23. Half-life - the time required for half the
concentration of an element to decompose.
Ex. If the mass of a radioisotope is 2.464 g, what
mass will remain after 6.0 h, if the half-life is 2.0 h,
and no more radioisotope is added.
mfinal = minitial (0.5)T/x x=duration of half-life
mfinal = 2.464g (0.5)6.0/2.0
= 2.464g (0.5)3.0
= 0.308g
= 0.31g
Therefore 0.31g of radioisotope remains
NUCLEAR REACTIONS
24. NUCLEAR REACTIONS
Artificial Transmutation
Alchemists never did turn lead into gold, but along the
way made many other discoveries about elements and
compounds. This was the origin of the science of
chemistry!
In artificial transmutation, a nucleus is hit by a small
nuclear particle moving at very high speed. This can
produce atoms with a desired number of protons and
neutrons.
27
13Al + 4
2He → 30
15P + 1
0n
We can now turn lead into gold!
31. NUCLEAR REACTIONS
8.9-scale earthquake threatens safety of nuclear power plants in
Japan (March 2011)
The earthquake and tsunami knocked out cooling systems
and fuel rods began overheating
In fission weapons, a mass of fissile material (enriched uranium or plutonium) is assembled into a supercritical mass—the amount of material needed to start an exponentially growing nuclear chain reaction—either by shooting one piece of sub-critical material into another (the "gun" method) or by compressing a sub-critical sphere of material using chemical explosives to many times its original density (the "implosion" method). The latter approach is considered more sophisticated than the former and only the latter approach can be used if the fissile material is plutonium.
