This document discusses molecular shape and polarity. It explains that polarity depends on polar bonds and molecular symmetry. A polar molecule has polar bonds whose dipoles do not cancel out, while a nonpolar molecule has either nonpolar bonds or polar bonds whose dipoles cancel out. It provides steps to determine polarity: draw Lewis structures, use VSEPR to predict shape, determine bond polarity from electronegativity differences, and add bond dipoles. Symmetric molecules with identical bonds are nonpolar as the dipoles cancel. Asymmetric molecules or those with different bond polarities, like NH3, are polar.
Polar and nonpolar bonds and polar molecules970245
polar and nonpolar bonds are explained with example and practice work is also given diplole action is explained. polar and non-polar molecules explained.
This power point work describe about polar and nonn polar compounds and how to find it very easily and it also explain dipole moment and its calculation...this includes some workout problems
Polar and nonpolar bonds and polar molecules970245
polar and nonpolar bonds are explained with example and practice work is also given diplole action is explained. polar and non-polar molecules explained.
This power point work describe about polar and nonn polar compounds and how to find it very easily and it also explain dipole moment and its calculation...this includes some workout problems
A very basic look at the dative covalent bond. It is normally met at CAPE, but recently has been introduced to students in form three. It is that form three occurrence which really prompted this piece of work
A very basic look at the dative covalent bond. It is normally met at CAPE, but recently has been introduced to students in form three. It is that form three occurrence which really prompted this piece of work
Project Leonardo da Vinci 2013, mobility of a Romanian delegation of experts in education from Bucharest, Romania at Dundee and Angus College, Scotland UK
The polarity of a molecule is determined by its molecular structure and the distribution of electrons within that structure. Polarity arises from differences in electronegativity between the atoms in a molecule. Electronegativity is a measure of an atom's ability to attract and hold onto electrons. When two atoms with different electronegativities bond together, the electrons in the bond are not shared equally, leading to an uneven distribution of charge within the molecule.
Polar Molecules: When there is an uneven distribution of charge within a molecule due to differences in electronegativity, the molecule is said to be polar. This results in a separation of charges, with one end of the molecule having a partial positive charge (δ+) and the other end having a partial negative charge (δ-).
Nonpolar Molecules: Nonpolar molecules have an even distribution of charge, meaning there are no significant differences in electronegativity between the atoms. As a result, there is no separation of charges within the molecule.
Electronegativity: The electronegativity of an atom is determined by the periodic table, and elements with higher electronegativities tend to attract electrons more strongly. The electronegativity difference between atoms in a bond is a key factor in determining the molecule's polarity.
Symmetry: In some cases, a molecule may have polar bonds but still be nonpolar overall due to its molecular geometry. If the polar bonds are arranged symmetrically so that the dipole moments cancel each other out, the molecule is nonpolar.
Dipole Moment: The dipole moment of a molecule is a measure of its polarity. It is a vector quantity that points from the positive end (δ+) to the negative end (δ-) of the molecule. A larger dipole moment indicates a more polar molecule.
Examples:
Water (H2O) is a polar molecule because oxygen is more electronegative than hydrogen, creating a significant dipole moment.
Carbon tetrachloride (CCl4) is a nonpolar molecule even though it has polar C-Cl bonds because the tetrahedral arrangement of the chlorine atoms results in cancellation of the dipole moments.
Solubility and Intermolecular Interactions: The polarity of a molecule plays a crucial role in its interactions with other molecules. Polar molecules tend to be soluble in polar solvents, while nonpolar molecules are more soluble in nonpolar solvents. Additionally, polar-polar interactions (dipole-dipole interactions) and nonpolar-nonpolar interactions (Van der Waals forces) are significant in determining the physical properties of substances.
Understanding the polarity of molecules is important in various fields, including chemistry, biology, and materials science, as it helps explain and predict the behavior of substances in chemical reactions and physical processes.
What is tetrahedron,a trigonal bipyramid, and an octahedron? In this lesson you will be able to: apply the valence shell electron pair repulsion theory to predict the molecular geometry of simple molecules; define dipole moment; predict the polarity of molecules.
This pdf is about the Schizophrenia.
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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.
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.
(May 29th, 2024) Advancements in Intravital Microscopy- Insights for Preclini...Scintica Instrumentation
Intravital microscopy (IVM) is a powerful tool utilized to study cellular behavior over time and space in vivo. Much of our understanding of cell biology has been accomplished using various in vitro and ex vivo methods; however, these studies do not necessarily reflect the natural dynamics of biological processes. Unlike traditional cell culture or fixed tissue imaging, IVM allows for the ultra-fast high-resolution imaging of cellular processes over time and space and were studied in its natural environment. Real-time visualization of biological processes in the context of an intact organism helps maintain physiological relevance and provide insights into the progression of disease, response to treatments or developmental processes.
In this webinar we give an overview of advanced applications of the IVM system in preclinical research. IVIM technology is a provider of all-in-one intravital microscopy systems and solutions optimized for in vivo imaging of live animal models at sub-micron resolution. The system’s unique features and user-friendly software enables researchers to probe fast dynamic biological processes such as immune cell tracking, cell-cell interaction as well as vascularization and tumor metastasis with exceptional detail. This webinar will also give an overview of IVM being utilized in drug development, offering a view into the intricate interaction between drugs/nanoparticles and tissues in vivo and allows for the evaluation of therapeutic intervention in a variety of tissues and organs. This interdisciplinary collaboration continues to drive the advancements of novel therapeutic strategies.
Earliest Galaxies in the JADES Origins Field: Luminosity Function and Cosmic ...Sérgio Sacani
We characterize the earliest galaxy population in the JADES Origins Field (JOF), the deepest
imaging field observed with JWST. We make use of the ancillary Hubble optical images (5 filters
spanning 0.4−0.9µm) and novel JWST images with 14 filters spanning 0.8−5µm, including 7 mediumband filters, and reaching total exposure times of up to 46 hours per filter. We combine all our data
at > 2.3µm to construct an ultradeep image, reaching as deep as ≈ 31.4 AB mag in the stack and
30.3-31.0 AB mag (5σ, r = 0.1” circular aperture) in individual filters. We measure photometric
redshifts and use robust selection criteria to identify a sample of eight galaxy candidates at redshifts
z = 11.5 − 15. These objects show compact half-light radii of R1/2 ∼ 50 − 200pc, stellar masses of
M⋆ ∼ 107−108M⊙, and star-formation rates of SFR ∼ 0.1−1 M⊙ yr−1
. Our search finds no candidates
at 15 < z < 20, placing upper limits at these redshifts. We develop a forward modeling approach to
infer the properties of the evolving luminosity function without binning in redshift or luminosity that
marginalizes over the photometric redshift uncertainty of our candidate galaxies and incorporates the
impact of non-detections. We find a z = 12 luminosity function in good agreement with prior results,
and that the luminosity function normalization and UV luminosity density decline by a factor of ∼ 2.5
from z = 12 to z = 14. We discuss the possible implications of our results in the context of theoretical
models for evolution of the dark matter halo mass function.
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 .
2. • Molecules in which the charge is not distributed
symmetrically among the atoms making up the molecule
• Polarity of molecule is dependent on the presence of polar
bonds & the shape of the molecule
WHAT ARE POLAR MOLECULES?
3. • ΔEN between 2 atoms determines the polarity of the bond –
greater the difference, the more polar the bond
BOND POLARITY
4. • Bond in which unequal sharing of electrons exists
• Electrons spend most of their time closer to one nucleus than
the other
POLAR COVALENT BONDS
5. • Polar covalent bonds are shown by using a bond dipole
(arrow indicating a ΔEN travelling from the lower (δ+
) to the
higher (δ-
) EN)
• The bond dipole is a vector, and vectors can be added (tip-to-
tail) to determine the overall polarity of a molecule
POLAR COVALENT BONDS
7. A molecule may have polar bonds, but it may not
be polar
Example:
CO2 is a nonpolar molecule, but each C=O bond is
polar
DETERMINING THE POLARITY OF A MOLECULE
8. • Existence of a polar bond in a molecules does not necessarily
mean the molecule is polar (also must consider symmetry)
• Nonpolar molecule: either has nonpolar bonds or polar bonds
whose dipoles cancel to zero
• Polar molecule: has polar bonds with dipoles that do not
cancel to zero
DETERMINING THE POLARITY OF A MOLECULE
9. 1. Draw a Lewis structure
2. Use the # of electron pairs &
VSEPR to determine the
shape around each central
atom
3. Use EN differences to
determine the polarity of
each bond
4. Add the bond dipole vectors
to determine if the final
result is zero (nonpolar
molecule) or non-zero (polar
molecule)
HOW TO DETERMINE THE POLARITY OF A MOLECULE
Example: CO2
Linear
Nonpolar
ΔEN = 1.0
3.5 2.5 3.5
δ+
δ-
δ-
10. 1. Draw a Lewis structure
2. Use the # of electron pairs &
VSEPR to determine the
shape around each central
atom
3. Use EN differences to
determine the polarity of
each bond
4. Add the bond dipole vectors
to determine if the final
result is zero (nonpolar
molecule) or non-zero (polar
molecule)
HOW TO DETERMINE THE POLARITY OF A MOLECULE
Example: H2O
Angular/bent
Polar
2.12.1
3.5
ΔEN = 1.4
12. HOW TO DETERMINE THE POLARITY OF A MOLECULE
Example: CO2 vs. H2O
13. • Can be difficult to add 3-D vectors so can use symmetry of the
molecule instead to determine its polarity
• In all symmetrical molecules, the sum of the bond dipoles is
zero & the molecule is nonpolar
SYMMETRY AND POLARITY
15. Is the shape
symmetrical
in 3D?
The molecule
is polar.
Are all the
∆EN bond
values the
same?
The molecule
is non-polar.
NO YES
bent
trigonal pyramidal
linear
tetrahedral
NO
YES
SYMMETRY AND POLARITY
Summary
18. Example: NH3
1) Draw the Lewis structure
2) Based on the Lewis structure, draw the VSEPR
diagram
MOLECULAR SHAPE AND POLARITY
19. 3) Add the electronegativity of
the atoms and assign δ+
and δ-
to the bonds
.: NH3 is polar because it has
polar bonds
that do no cancel to zero.
4) Draw in the bond dipoles
Example: NH3
MOLECULAR SHAPE AND POLARITY