Chemical bonds result from the attraction between positively charged nuclei and negatively charged electrons. There are three main types of bonding: ionic, metallic, and covalent. Ionic bonding involves the transfer of electrons between atoms to form ions with opposite charges that are attracted to each other. Covalent bonding involves the sharing of electrons between nonmetal atoms. Molecules form through covalent bonds and have molecular formulas that describe the number and type of atoms present. The shape and polarity of molecules can be predicted from their Lewis structures.
Sexual reproduction is a biological process by which offspring are produced by the combination of genetic material from two parent organisms. It involves the fusion of specialized reproductive cells called gametes, which typically come from two different individuals of the same species.
Gamete Formation: Each parent produces specialized reproductive cells called gametes. In most animals, the male parent produces small, mobile gametes called sperm, while the female parent produces larger, usually immobile gametes called eggs. In plants, the male gamete is typically contained within pollen grains, and the female gamete is located within ovules.
Fertilization: The gametes from the male and female parents fuse during fertilization, forming a zygote. This process usually occurs through the union of the sperm and egg. Fertilization typically occurs externally in many aquatic organisms and internally in most terrestrial organisms.
Genetic Variation: One of the key features of sexual reproduction is the generation of genetic diversity. Offspring produced through sexual reproduction inherit genetic material from both parents, leading to genetic variation among individuals within a population. This genetic diversity is important for the adaptation and evolution of species over time.
Meiosis: In preparation for sexual reproduction, specialized cell division called meiosis occurs in the cells that give rise to gametes. Meiosis ensures that the resulting gametes contain only half the number of chromosomes found in other body cells, allowing the union of gametes to restore the full chromosome number in the zygote.
Sexual reproduction is the predominant mode of reproduction in multicellular organisms, including most animals, plants, and fungi. It offers several advantages, such as genetic diversity, which enhances the ability of organisms to adapt to changing environments and improves the overall fitness of populations.
Sexual reproduction is common in many multicellular organisms, including animals, plants, and fungi. It contrasts with asexual reproduction, where offspring are produced from a single parent and are genetically identical or very similar to that parent. The diversity introduced by sexual reproduction is advantageous for evolutionary processes, as it can lead to individuals with new combinations of traits that may be better adapted to changing environments.
The organ system of animals is a complex network of specialized structures working together to support life functions, maintain homeostasis, and enable organisms to interact with their environment. Organ systems are comprised of organs, tissues, and cells, each with unique roles and functions that contribute to the overall health and survival of the organism.
Animals exhibit a remarkable diversity of organ systems, reflecting their adaptation to different ecological niches, lifestyles, and evolutionary histories. While specific structures may vary among species, most animals share several fundamental organ systems essential for survival. These include the digestive system, respiratory system, circulatory system, nervous system, muscular system, skeletal system, excretory system, reproductive system, and endocrine system.
Sexual reproduction is a biological process by which offspring are produced by the combination of genetic material from two parent organisms. It involves the fusion of specialized reproductive cells called gametes, which typically come from two different individuals of the same species.
Gamete Formation: Each parent produces specialized reproductive cells called gametes. In most animals, the male parent produces small, mobile gametes called sperm, while the female parent produces larger, usually immobile gametes called eggs. In plants, the male gamete is typically contained within pollen grains, and the female gamete is located within ovules.
Fertilization: The gametes from the male and female parents fuse during fertilization, forming a zygote. This process usually occurs through the union of the sperm and egg. Fertilization typically occurs externally in many aquatic organisms and internally in most terrestrial organisms.
Genetic Variation: One of the key features of sexual reproduction is the generation of genetic diversity. Offspring produced through sexual reproduction inherit genetic material from both parents, leading to genetic variation among individuals within a population. This genetic diversity is important for the adaptation and evolution of species over time.
Meiosis: In preparation for sexual reproduction, specialized cell division called meiosis occurs in the cells that give rise to gametes. Meiosis ensures that the resulting gametes contain only half the number of chromosomes found in other body cells, allowing the union of gametes to restore the full chromosome number in the zygote.
Sexual reproduction is the predominant mode of reproduction in multicellular organisms, including most animals, plants, and fungi. It offers several advantages, such as genetic diversity, which enhances the ability of organisms to adapt to changing environments and improves the overall fitness of populations.
Sexual reproduction is common in many multicellular organisms, including animals, plants, and fungi. It contrasts with asexual reproduction, where offspring are produced from a single parent and are genetically identical or very similar to that parent. The diversity introduced by sexual reproduction is advantageous for evolutionary processes, as it can lead to individuals with new combinations of traits that may be better adapted to changing environments.
The organ system of animals is a complex network of specialized structures working together to support life functions, maintain homeostasis, and enable organisms to interact with their environment. Organ systems are comprised of organs, tissues, and cells, each with unique roles and functions that contribute to the overall health and survival of the organism.
Animals exhibit a remarkable diversity of organ systems, reflecting their adaptation to different ecological niches, lifestyles, and evolutionary histories. While specific structures may vary among species, most animals share several fundamental organ systems essential for survival. These include the digestive system, respiratory system, circulatory system, nervous system, muscular system, skeletal system, excretory system, reproductive system, and endocrine system.
A brief information about the SCOP protein database used in bioinformatics.
The Structural Classification of Proteins (SCOP) database is a comprehensive and authoritative resource for the structural and evolutionary relationships of proteins. It provides a detailed and curated classification of protein structures, grouping them into families, superfamilies, and folds based on their structural and sequence similarities.
What is greenhouse gasses and how many gasses are there to affect the Earth.moosaasad1975
What are greenhouse gasses how they affect the earth and its environment what is the future of the environment and earth how the weather and the climate effects.
(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.
Professional air quality monitoring systems provide immediate, on-site data for analysis, compliance, and decision-making.
Monitor common gases, weather parameters, particulates.
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 .
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.
Cancer cell metabolism: special Reference to Lactate PathwayAADYARAJPANDEY1
Normal Cell Metabolism:
Cellular respiration describes the series of steps that cells use to break down sugar and other chemicals to get the energy we need to function.
Energy is stored in the bonds of glucose and when glucose is broken down, much of that energy is released.
Cell utilize energy in the form of ATP.
The first step of respiration is called glycolysis. In a series of steps, glycolysis breaks glucose into two smaller molecules - a chemical called pyruvate. A small amount of ATP is formed during this process.
Most healthy cells continue the breakdown in a second process, called the Kreb's cycle. The Kreb's cycle allows cells to “burn” the pyruvates made in glycolysis to get more ATP.
The last step in the breakdown of glucose is called oxidative phosphorylation (Ox-Phos).
It takes place in specialized cell structures called mitochondria. This process produces a large amount of ATP. Importantly, cells need oxygen to complete oxidative phosphorylation.
If a cell completes only glycolysis, only 2 molecules of ATP are made per glucose. However, if the cell completes the entire respiration process (glycolysis - Kreb's - oxidative phosphorylation), about 36 molecules of ATP are created, giving it much more energy to use.
IN CANCER CELL:
Unlike healthy cells that "burn" the entire molecule of sugar to capture a large amount of energy as ATP, cancer cells are wasteful.
Cancer cells only partially break down sugar molecules. They overuse the first step of respiration, glycolysis. They frequently do not complete the second step, oxidative phosphorylation.
This results in only 2 molecules of ATP per each glucose molecule instead of the 36 or so ATPs healthy cells gain. As a result, cancer cells need to use a lot more sugar molecules to get enough energy to survive.
Unlike healthy cells that "burn" the entire molecule of sugar to capture a large amount of energy as ATP, cancer cells are wasteful.
Cancer cells only partially break down sugar molecules. They overuse the first step of respiration, glycolysis. They frequently do not complete the second step, oxidative phosphorylation.
This results in only 2 molecules of ATP per each glucose molecule instead of the 36 or so ATPs healthy cells gain. As a result, cancer cells need to use a lot more sugar molecules to get enough energy to survive.
introduction to WARBERG PHENOMENA:
WARBURG EFFECT Usually, cancer cells are highly glycolytic (glucose addiction) and take up more glucose than do normal cells from outside.
Otto Heinrich Warburg (; 8 October 1883 – 1 August 1970) In 1931 was awarded the Nobel Prize in Physiology for his "discovery of the nature and mode of action of the respiratory enzyme.
WARNBURG EFFECT : cancer cells under aerobic (well-oxygenated) conditions to metabolize glucose to lactate (aerobic glycolysis) is known as the Warburg effect. Warburg made the observation that tumor slices consume glucose and secrete lactate at a higher rate than normal tissues.
2. Chemical Bond
A Quick Review….
• A bond that results from the attraction of
nuclei for electrons
• IN OTHER WORDS
– the protons (+) in one nucleus are attracted to
the electrons (-) of another atom
• This is Electronegativity !!
2
4. Three Major Types of Bonding
1.Ionic Bonding
–forms ionic compounds
–transfer of valence electron
2. Metallic Bonding
- formed between two metals
3. Covalent Bonding
–forms molecules
–sharing of valence electron
4
5. 5
What is an Ionic Bond?
An ionic bond is a type of
chemical bond formed by
electrostatic attraction between
two oppositely-charged ions.
These ions are created by the
transfer of valence electrons
between two atoms, usually a
metal and a non-metal.
6. 1. Ionic Bonding
• Always formed between metal cations
and non-metals anions
• Cations are ions that are positively
charged. Anions are ions that are
negatively charged
• The oppositely charged ions stick like
magnets
[METALS ]+ [NON-METALS ]-
Lost e- Gained e- 6
7. • During ionic bonding, two atoms
(usually a metal and a non-metal)
exchange valence electrons. One
atom acts as an electron donor,
and the other as an electron
acceptor.
• This process is called electron
transfer and creates two
oppositely-charged ions. 8
8. • For example, when a sodium atom meets
a chlorine atom, the sodium donates one
valence electron to the chlorine.
• This creates a positively-charged sodium
ion and a negatively-charged chlorine ion.
• The electrostatic attraction between them
forms an ionic bond, resulting in a stable
ionic compound called sodium chloride
(AKA table salt).
10
11. 2. Metallic Bonding
• Always formed between 2 metals (pure
metals)
– Solid gold, silver, lead, etc…
14
12. 3. Covalent Bonding
• Pairs of electrons
are shared
between 2 non-
metal atoms to
acquire the electron
configuration of a
noble gas.
molecules
15
13. Covalent Bonding
• Occurs between nonmetal atoms which need to
gain electrons to get a stable octet of electrons
or a filled outer shell.
• The octet rule refers to the tendency of atoms
to prefer to have eight electrons in the valence
shell. When atoms have fewer than eight
electrons, they tend to react and form more
stable compounds.
• The outermost shell of any atom is called the
valence shell and the electrons that reside in
the valence shell are called valence electrons
14. Drawing molecules (covalent)
using Lewis Dot Structures
• Symbol represents the KERNEL of the atom
(nucleus and inner electrons)
• dots represent valence electrons
• Draw a valence electron on each side (top, right,
bottom, left) before pairing them.
17
15. Always remember atoms are trying
to complete their valence shell!
“2 will do but 8 is great!”
The number of electrons the atom needs is the
total number of bonds they can make.
Ex. … H? O? F? N? Cl? C?
one two one three one four
18
16. Draw Lewis Dot Structures
You may represent valence electrons
from different atoms with the
following symbols x, ,
H or H or H
x
19
17. • The atoms form a covalent bond by
sharing their valence electrons to
get a stable octet of electrons.(filled
valence shell of 8 electrons)
• Electron-Dot Diagrams of the atoms
are combined to show the covalent
bonds
• Covalently bonded atoms form
MOLECULES
18. Methane CH4
• This is the finished Lewis dot structure
• Every atom has a filled valence shell
How did we get here?
OR
21
19. General Rules for Drawing Lewis Structures
• All valence electrons of the atoms in Lewis structures must
be shown.
• Generally each atom needs eight electrons in its valence
shell (except Hydrogen needs only two electrons and
Boron needs only 6).
• Multiple bonds (double and triple bonds) can be formed by
C, N, O, P, and S.
• Central atoms have the most unpaired electrons.
• Terminal atoms have the fewest unpaired electrons.
22
20. • When carbon is one of your atoms, it will
always be in the center
• Sometimes you only have two atoms, so
there is no central atom
Cl2 HBr H2 O2 N2 HCl
• We will use a method called ANS
(Available, Needed, Shared) to help us draw
our Lewis dot structures for molecules
23
21. EXAMPLE 1: Write the Lewis structure for H2O where oxygen is the central atom.
Step 1: Determine the total number of electrons available for bonding. Because only valence
electrons are involved in bonding we need to determine the total number of valence electrons.
AVAILABLE valenceelectrons:
Electrons available
2 H Group 1 2(1) = 2
O Group 6 6
8
There are 8 electrons available for bonding.
Step 2: Determine the number of electrons needed by
each atom to fill its valence shell.
NEEDED valence electrons
Electrons needed
2 H each H needs 2 2(2) = 4
O needs 8 8
12
There are 12 electrons needed.
24
22. Step 3: More electrons are needed then there are available. Atoms therefore make bonds by sharing
electrons. Two electrons are shared per bond.
SHARED (two electrons per bond)
# of bonds = (# of electrons needed – # of electrons available) = (N-A) = (12 – 8) = 2 bonds.
2 2 2
Draw Oxygen as the central atom. Draw the Hydrogen atoms on either side of the oxygen atom.
Draw the 2 bonds that can be formed to connect the atoms.
OR
Step 4: Use remaining available electrons to fill valence shells for each atom. All atoms need 8 electrons
to fill their valence shell (except hydrogen needs only 2 electrons to fill its valence shell, and
boron only needs 6). For H2O there are 2 bonds, and 2 electrons per bond.
# available electrons remaining = # electrons available – # electrons shared = A-S = 8 – 2(2) = 4 extra e-
s
25
23. Sometimes multiple bonds must be formed to get
the numbers of electrons to work out
• DOUBLE bond
– atoms that share two e- pairs (4 e-)
O O
• TRIPLE bond
– atoms that share three e- pairs (6 e-)
N N 26
25. Step 3: SHARED (two electrons per bond)
# of bonds = (N – A) = (20 – 12) = 4 bonds.
2 2
Draw carbon as the central atom (Hint: carbon is always the center when it is present!). Draw the
Hydrogen atoms and oxygen atom around the carbon atom. Draw 2 bonds of the 4 bonds that can
be formed to connect the H atoms. Draw the remaining 2 bonds to connect the O atom (oxygen
can form double bonds)
Step 4: Use remaining available electrons to fill valence shell for each atom.
# electrons remaining = Available – Shared = A – S = 12 – 4(2) = 4 extra e-
s
28
26. Let’s Practice
H2
A = 1 x 2 = 2
N = 2 x 2 = 4
S = 4 - 2= 2 ÷ 2 = 1 bond
Remaining = A – S = 2 – 2 = 0
DRAW
29
27. Let’s Practice
CH4
A = C 4x1 = 4 H 1x4 = 4 4 + 4 = 8
N = C 8x1 = 8 H 2x4 = 8 8 + 8 = 16
S = (N-A)16 – 8 = 8 ÷2 = 4 bonds
Remaining = A-S = 8 – 8 = 0
DRAW
30
28. Let’s Practice
NH3
A = N 5x1 = 5 H 1x3 = 3 = 8
N = N 8x1 = 8 H 2x3 = 6 = 14
S = 14-8 = 6 ÷2 = 3 bonds
Remaining = (A-S) 8 – 6 = 2
DRAW
31
29. Let’s Practice
CO2
A = C 4x1 = 4 O 6x2 = 12 = 16
N = C 8x1 = 8 O 8x2 = 16 = 24
S = 24-16 = 8 ÷ 2 = 4 bonds
Remaining = (A-S) 16 – 8 = 8 not bonding
DRAW – carbon is the central atom
32
30. Let’s Practice
BCl3 boron only needs 6 valence electrons, it is an exception.
A = B 3 x 1 = 3 Cl 7 x 3 = 21 = 24
N = B(6) x 1 = 6 Cl 8 x 3 = 24 = 30
S = 30-24 = 6 ÷ 2 = 3 bonds
Remaining = 24 – 6 = 18 e- not bonding
DRAW
33
39. Rules for Naming
Molecular compounds
• The most “metallic” nonmetal
element is written first (the one that
is furthest left)
• The most nonmetallic of the two
nonmetals is written last in the
formula
• NO2 not O2N
• All binary molecular compounds end
in -ide
40. • Ionic compounds use charges to determine the
chemical formula
• The molecular compound‘s name tells you the
number of each element in the chemical
formula.
• Uses prefixes to tell you the quantity of each
element.
• You need to memorize the prefixes !
Molecular compounds
42. • If there is only one of the first element do
not put (prefix) mono
• Example: carbon monoxide (not monocarbon monoxide)
• If the nonmetal starts with a vowel, drop
the vowel ending from all prefixes except
di and tri
• monoxide not monooxide
• tetroxide not tetraoxide
More Molecular Compound Rules
67. Ionic Character
“Ionic Character” refers to a bond’s
polarity
–In a polar covalent bond,
•the closer the EN difference is to 2.0,
the more POLAR its character
•The closer the EN difference is to .20,
the more NON-POLAR its character
71
68. Place these molecules in order of increasing
bond polarity using the electronegativity
values on your periodic table
• HCl
• CH4
• CO2
• NH3
• N2
• HF
a.k.a.
“ionic character”
72
1 EN difference = 0
2 EN difference = 0.4
3 EN difference = 0.9
4 EN difference = 1.0
3 EN difference = 0.9
5 EN difference = 1.9
69. Polar vs. Nonpolar
MOLECULES
• Sometimes the bonds within a
molecule are polar and yet the
molecule itself is non-polar
73
70. Nonpolar Molecules
• Molecule is Equal on all sides
–Symmetrical shape of molecule
(atoms surrounding central atom are
the same on all sides)
H
H
H
H C
Draw Lewis dot first and
see if equal on all sides
74
71. Polar Molecules
• Molecule is Not Equal on all sides
–Not a symmetrical shape of molecule
(atoms surrounding central atom are
not the same on all sides)
Cl
H
H
H C
75
76. H
H
O
Water is a POLAR molecule
ANY time there are unshared pairs
of electrons on the central atom, the
molecule is POLAR
80
77. Making sense of the polar
non-polar thing
BONDS
Non-polar Polar
EN difference EN difference
0 - .2 .21 – 1.99
MOLECULES
Non-polar Polar
Symmetrical Asymmetrical
OR
Unshared e-s on
Central Atom
81
78. 5 Shapes of Molecules
you must know!
(memorize)
82
79. Copy this slide
• VSEPR – Valence Shell Electron Pair
Repulsion Theory
– Covalent molecules assume geometry
that minimizes repulsion among electrons
in valence shell of atom
– Shape of a molecule can be predicted
from its Lewis Structure
83
80. 1. Linear (straight line)
Ball and stick
model
Molecule geometry X A X
OR
A X
Shared Pairs = 2 Unshared Pairs = 0
OR
84
81. 2. Trigonal Planar
Ball and stick
model
Molecule geometry X
A
X X
Shared Pairs = 3 Unshared Pairs = 0 85
85. • I can describe the 3 intermolecular
forces of covalent compounds and
explain the effects of each force.
89
86. • Attractions
within or inside
molecules, also
known as bonds.
– Ionic
– Covalent
– metallic
Intramolecular attractions
90
Roads within a state
87. • Attractions between
molecules
– Hydrogen “bonding”
• Strong attraction
between special polar
molecules (F, O, N, P)
– Dipole-Dipole
• Result of polar covalent
Bonds
– Induced Dipole
(Dispersion Forces)
• Result of non-polar
covalent bonds
Intermolecular attractions
91
88. More on intermolecular forces
Hydrogen “Bonding”
• STRONG
intermolecular force
– Like magnets
• Occurs ONLY
between H of one
molecule and N, O,
F of another
molecule
Hydrogen
“bond”
-
+
+
-
+ +
+
+
-
92
Hydrogen bonding
1 min
89. Why does Hydrogen
“bonding” occur?
• Nitrogen, Oxygen and Fluorine
– are small atoms with strong nuclear
charges
• powerful atoms
– Have very high electronegativities,
these atoms hog the electrons in a bond
– Create very POLAR molecules
93
90. Dipole-Dipole Interactions
– WEAK intermolecular force
– Bonds have high EN differences
forming polar covalent molecules,
but not as high as those that result
in hydrogen bonding.
.21<EN<1.99
– Partial negative and partial
positive charges slightly attracted
to each other.
– Only occur between polar
covalent molecules
94
92. Induced Dipole Attractions
– VERY WEAK intermolecular force
– Bonds have low EN differences EN < .20
– Temporary partial negative or positive charge
results from a nearby polar covalent molecule.
– Only occur between NON-POLAR & POLAR
molecules
96
Induced dipole video
30 sec
94. Intermolecular Forces
affect chemical properties
• For example, strong intermolecular
forces cause high Boiling Point
– Water has a high boiling point compared
to many other liquids
98
96. Which substance has the
highest boiling point?
• HF
• NH3
• CO2
• WHY?
The H-F bond has the highest
electronegativity difference
SO
HF has the most polar bond
resulting in the strongest H
bonding (and therefore needs the
most energy to overcome the
intermolecular forces and boil)
100