THE MATRIX
NANOSTRUCTURE ELECTROSTATIC INTERACTIONS ENERGY
There are two types of electrostatic interactions:
attraction and repulsion
The unbound atom
The charged particles The charged particles Nanostructure - electron population technique
In each energy level there is a specific number of
Protons are positive Protons are positive
orbitals
Each orbital is populated by 1 or 2 electrons at the
Electrons are negative Electrons are negative
most
Nuclei are positive Nuclei are positive Lower energy levels get filled before higher ones
The charge of the nucleus equals the number of The charge of the nucleus is defined by the number Empty orbitals get filled before partially populated
protons of protons orbitals in the same energy level
The maximum number of electrons in the first
In a neutral atom the number of electrons equals In a neutral atom the number of electrons equals
energy level is 2, in the second energy level is 8, in
the number of protons the number of protons
the third energy level is 8 (till atomic number 18)
If the number of electrons differs the number of If the number of electrons differs the number of
Energy levels in the atom
protons, the atom is charged and it is called a ion protons, the atom is charged and it is called a ion
Positive ions have fewer electrons than protons, Positive ions have fewer electrons than protons, Electrons are found around the nucleus in energy
Negative ions have more electrons than protons Negative ions have more electrons than protons levels
Momentary partial charges (δ- and δ+) in the Momentary partial charges (δ- and δ+) in the
The distance of an electron from the nucleus is
electron cloud are caused because electrons have electron cloud are caused because electrons have
determined by its energy
no fixed position no fixed position
Momentary partial charges (δ- and δ+ ) in the Momentary partial charges (δ- and δ+ ) in the
In average, electron populating lower energy levels
electron cloud are caused due to momentary electron cloud are caused due to momentary
are closer to the nucleus than those populating
asymmetric changes in the distribution of the asymmetric changes in the distribution of the
higher energy levels
electrons electrons
The valence electrons are the electrons populating
the outer highest energy level
Particles with full energy levels are less reactive
than those with partly full energy levels
Nanostructure Description of interactions Ionization energy
Energy is needed to separate an electron from its
Nuclei consist of protons and neutrons
atom (ionization energy)
The ionization energy increases as the attraction
There is an electrical attraction between the
Atoms consist of nuclei and electrons force between the nucleus and the electron
nucleus and electrons
increases
There is an electrical repulsion between the
Electrons move around the nucleus
electrons
Atoms are not small balls (they don't have a
border)
Electrons do not move in “orbits” around the
nucleus (Rutherford’s model)
Electrons are found at different distances around Bohr's model doesn't explain why electrons don't
the nucleus (Bohr’s model) stick to the nuclei
The valence electrons are the electrons in the outer
populated energy level
The attraction between the nucleus and electrons
Atoms are mostly vacuum
hold the atom together
Electrons have no fixed position in the atom, but Momentary partial charges (δ- and δ+ ) in the
can be found everywhere in the electron cloud (a electron cloud are possible because electrons have
region) at once no fixed position and repel each other
Electrons have no fixed position, but rather are
distributed in a probabilistic fashion
An orbital is the space in which there is a high
probability to find electrons
The shape of an atom is defined by the shape of its
electron populated cloud
The size of an atom (its radius) is determined
mainly by its number of populated energy levels
The size of an atom (its radius) decreases as the
nucleus charge increases among atoms with same
number of populated energy levels
The Lewis Formula represents the valence
electrons
Magnitude of interaction between nuclei and
Periodic Table (PT) The Periodic Table (PT) & ionization energy
electrons (Coulomb's law)
Coulomb's law (declarative, operational and high)
The number of valence electrons equals the group
number in the PT
The attraction force between a nucleus and an Ionization energy of a valence electron decreases
The number of populated energy levels equals the
electron increases as the number of energy level in as the number of populated energy levels increases
row number in the PT
which the electron is decreases (along a column of the PT)
The attraction force between a nucleus and an Ionization energy decreases along a column in the
electron increases as the distance between them PT as the distance between the nucleus and
decreases valence electrons increases
The attraction force between a nucleus and an Along a row in the PT, the general trend is that
The atomic number equals the number of protons external level electron increases as the atomic ionization energy increases as the nucleus charge
number increases among particles of similar size. increases
When comparing the ionization energy of similar
The attraction force between nucleus and external size atoms (radius), the general trend is that the
level electron increases as nucleus charge increases ionization energy of the valence electron
among particles of similar size. occupying the same energy level increases as the
nucleus charge increases
The repulsion force between the electrons
populating the same energy level increases as their
number increases because the distance between
them decreases
The size of the atom (radius) decreases along the
The general trend is that the size of an atom PT row due to the increase in attraction force
decreases along the PT row between nucleus and electrons as nucleus' charge
increases
The number of valence electrons does not influence
the attraction force between the nucleus and each
valence electron
One bond between two atoms
The bound atom's characteristics Electronegativity (EN)
The number of protons doesn't change in chemical
reactions.
Atoms of different elements have a different
EN reflects the relative attraction between the
number of protons and electrons which influences
bonding electrons and the rest of the atom
their chemical activity
Atoms may form a single bond, a double bond, or a EN is influenced among other, by the energy of
triple bond. ionization and the electron affinity
An atom's valence electrons determine the number
The EN of an atom is influenced by the adjacent
of bonds an atom can form (in organic molecules)
bound atoms
according to the octet rule
General characteristics of the bond
Description of interactions (general) Description of the energy involved (general)
nanostructure
There is an electrical attraction force between
The bonding electrons are paired bonding electrons and the nuclei of the bound Energy is required to break a bond between atoms
atoms
The bonding electrons are shared forming a There is an electrical repulsion force between the
molecular orbital. non-bonding electrons of the bound atoms
A molecular orbital represents the probability to There is an electrical repulsion force between the
find electrons in the space around the bound atoms nuclei of the bound atoms
There is an electrical repulsion force between The energy required to break a chemical bond, to
bonding electrons separate the 2 atoms is the Bond energy
The energy required to break a bond into atoms is
There is mostly vacuum between nuclei in a bond equal to the energy released when the bond is
formed
Empty molecular orbitals get filled before partially
populated orbitals in the same energy level
The interaction between two atoms vs distance
between two nuclei (Coulomb's law)
At the bond length there is an equilibrium state
The bond length is the distance between nuclei at When 2 bound atoms are at bond length the system
because attraction forces are equal to repulsion
which the atoms are in equilibrium is at minimum energy
forces between the bound atoms
When two atoms move toward each other their Two atoms move toward each other because the
Two atoms bond if the energy of the bound atoms
orbitals overlap with each other forming a attraction forces are stronger than the repulsion
is lower than that of the two separated atoms
molecular orbital forces between them
At a closer distance than the bond length atoms
When 2 bound atoms are at bond length, energy is
move away from each other because, repulsion
required to separate or get the atoms closer to each
forces are stronger than attraction forces between
other
them
When the atoms are far from each other, the energy
When the bond is broken, the atoms are separated When the atoms are far from each other, any
of the system is given by the sum of the energy of
and the molecule is broken interaction- attraction or repulsion is negligible.
both atoms.
Electric forces between electrons and nucleus hold
bound atoms together at the bond length.
Types of chemical bonds - EN & electron Types of chemical bonds - EN & charge
distribution distribution
Thumb rule:
Non-metals form covalent bonds between In general, the EN of nonmetal atoms is higher than
themselves, Metals form ionic bonds with non- the EN of metal atoms
metals
There are permanent partial charges (δ- and δ+ ) in
Atoms with same EN form covalent (non polar)
the electron cloud due to the asymmetric
bonds
distribution of the electrons.
In covalent (non polar) bonds the probability of In covalent (non polar) bonds the bonding electrons
finding bonding electrons around both atoms is are equally shared because both atoms have the
equal same EN
In a Polar covalent bond, the electrons are not
Atoms with similar but not identical EN form polar
evenly shared; in average, the electrons are more
covalent bonds
attracted to the more electronegative atom
In polar covalent bonds the more EN atom is In polar covalent bonds the more EN atom is
partially negatively charged δ- and the less EN partially negatively charged δ- and the less EN
atom bound to it is partially positively charged δ+ atom bound to it is partially positively charged δ+
The probability of finding bonding electrons The polarity of the bond increases as the difference
around the more EN atom is greater in the EN of the bound atoms increases
Permanent partial charges are created due to the
In intramolecular bonds electrons are transferred or
asymmetric distribution of electrons in chemical
shared in molecular orbitals
bonds.
In Ionic bonds negative nonmetal ions and positive
metal ions can be assumed to exist since in bonds
Atoms with very different EN form ions, a negative
between atoms with very different EN bonding
nonmetal ion, a positive metal ion
electrons are not shared, but are mostly by the
electronegative atom
Ionic bonds are extreme cases of polar bonds. The
In ionic bonds the more EN atom is a negative ion, more electronegative atom is negatively charged (-)
the less EN atom is a positive ion. and the less electronegative atom bound to it is
positively charged (+)
Bond length bond strength, bond energy Magnitude of interaction (Coulomb's law ) Bond energy bond strength, bond length
In general, bond length decreases as the strength of The strength of a bond increases as the bond In general, bond energy increases as the bond
a bond and bond energy increase energy increases length decreases
In general, the strength of a bond or bond energy
increases as the bond length decreases
The strength of a bond is evaluated by its bond
The bond energy represents the bond strength
energy
The bond strength indicates the total attractive (and
repulsive) forces between the particles in the bound
atoms
The total attractive (and repulsive) forces (the bond
Bond length increases with increasing radius of the Bond energy increases with decreasing radius of
strength) increase with decreasing radius of the
bound atoms the bound atoms
bound atoms
The total attractive (and repulsive) forces (the bond
Bond length increases as the total attractive and Bond energy increases with increasing attractive
strength) increase as the distance between the
repulsive forces decrease and repulsive forces
bonding electrons and nuclei decreases
Bond length increases from triple to double to The strength of a bond increases from single to The bond energy increases from single to double
single bond (for the same atoms) double to triple (for the same atoms) to triple
The total attractive (and repulsive) forces increases
For similar size bound atoms, bond length
as the number of bonding electrons between two
increases as the number of lone pairs decreases
bound atoms increases
For similar size bound atoms, bond length For similar size bound atoms, the strength of a For similar size atoms, the bond energy increases
increases as the difference in EN decreases bond increases as the difference in EN increases as the difference in EN increases
In polar covalent bonds there is an electrical
attraction force between bonded positive δ+ and
negative δ- partially charged atoms
In an ionic bond, there is an electrical attraction
force between positive and negative ions
One molecule
Nanostructure
Once paired in a covalent bond electrons cannot Once paired in a covalent bond bonding electrons
take part in additional covalent bonds cannot take part in additional covalent bonds
In organic molecules the number of bonds that an
atom can form in a molecule depends on the Atoms can form a molecule if the energy of the
number of electrons required to complete its bound atoms (molecule) is lower than the sum of
valence energy level by sharing, transferring or the energies of the separated atoms
receiving electrons (octet rule)
In ionic bonds, the ions’ energy levels can be In ionic bonds, the ions’ energy levels can be
The basic building block of a substance is neutral
approximated as full and can be deduced by the PT approximated as full and can be deduced by the PT
Shape
Atoms bond into well defined shaped molecules The shape of a molecule is defined by electric forces
Molecules are not "rigid"
The shape of the molecule is determined by the
The shape and size of a molecule are defined by the The molecule’s geometrical structure is such that
VSEPR theory (repulsion of electron clouds-
size and shape of its electron cloud it is at minimum energy
orbitals)
In polar molecules there is a partially negatively
charged δ- side and a partially positively charged
δ+ side
The polarity of the molecule is determined by the The polarity of the molecule is determined by the
polarity of its bonds, its shape and its symmetry polarity of its bonds, its shape and its symmetry
Isomers are substances with the same molecular
formula but different structural formula
Representations and chemical formulas
Molecular formulas state the number and type of
atoms bound in a neutral molecule
In a Lewis Formula each atom in a molecule is
represented by its symbol and its valence electrons
The geometry of a molecule can be concluded from
a 2D Lewis formula,
Many bonds of the same type (lattice)
Nanostructure Interactions in nanostructure
Covalent lattices are solids at room temperature
In covalent, metallic and ionic solids molecular because the thermal energy available at room
In a covalent lattice atoms are covalently bound
"building blocks" cannot be identified temperature is not enough to break the covalent
bond
Most ionic substances are solids because the
In an ionic lattice, ions are ordered in a positive – In an ionic lattice, ions are ordered in a positive – thermal energy available at room temperature is not
negative pattern negative pattern due to electrostatic interaction. enough to separate the ions, although there are
ionic liquids as well
The structure of a lattice is such that it is at
minimum energy
Charged particles (charge distribution) Charged particles (charge distribution)
The delocalization of electrons in metals is due to
In metal lattices, bonding electrons are delocalized
the presence of conducting bands (overlapping
over ordered atoms (or ions).
orbitals)
In covalent lattices, the bonding electrons may be
localized or unlocalized.
Representations and chemical formulas
Empiric formulas represent the smallest and
whole ratio of the atoms or ions in a substance
Many bonds of different types
Description of the bound particles Interactions between bound particles
Van der Waal's forces are electrostatic interactions
Van der Waal's forces are electrostatic interactions
between molecules or individual atoms, caused by
between polar molecules, non polar molecules or
momentary or permanent polarization of
between individual atoms
molecules (δ- and δ+)
Hydrogen bonds are interactions between a
hydrogen atom (δ+)(commonly known as
"exposed" hydrogen”), that is bound covalently to
an EN atom (δ-) and another electronegative atom
(δ-) (H δ+ δ-X-H δ+)
The hydrogen atom participating in the hydrogen
bond is covalently bound to a very EN atom which
attracts the hydrogen's only electron, resulting in
big partial charges (H δ+ δ-X-H δ+ )
In a hydrogen bond the "exposed” hydrogen atom In a hydrogen bond the "exposed” hydrogen atom
binds to a lone pair of an EN atom which is not binds to a lone pair of an EN atom which is not
covalently bound to it (H δ+ δ-:X-H δ+) covalently bound to it (H δ+ δ-:X-H δ+)
Hydrogen bonds have H X-H 180o – a linear
Hydrogen bonds have a linear geometry H :X-H geometry which cannot be explained only by
electrostatic interactions
Van der Waal's forces are electrostatic interactions
Van der Waal's forces are electrostatic
between molecules or individual atoms, caused by
interactions between polar molecules, non polar
momentary or permanent polarization of
molecules or between individual atoms
molecules (δ- and δ+).
The shape, polarity and functional groups of the
molecule determine the interactions between
molecules
In heterogeneous mixtures no intermolecular
bonds occur between particles in the different
phases
In solutions, particles of different substances
(molecules, atoms or ions) bind by VDW,
In molecular substances the molecular "building
hydrogen bonds or other electrostatic interactions.
blocks" can be identified in all states of matter
The solute and the solvent particles bind to each
other
Magnitude of interaction (Fαqq)
The number of hydrogen bonds per molecule is
estimated by the smallest number between: The electrostatic interaction (VDW and Hydrogen The energy required to separate molecules increases
The number of non bonding electron pairs on the bonds) between molecules increases as the number with the number of permanent polar sites in the
electro-negative atom X per molecule (acceptor) of permanent polar sites in the molecules that are molecules (e.g.,the number of Hydrogen bonds per
The number of "exposed" H atoms per molecule. bound increases. molecule)
(donor)
The electrostatic interaction (VDW and Hydrogen The energy required to separate molecules
bond) between molecules increases as the increases as the magnitude of permanent polar sites
magnitude of the permanent polar sites in the in the molecules that interact increase. (e.g. A
molecules that are bound increase. E.g. A larger larger dipole moment is formed in OH than in NH
dipole moment is formed in OH than in NH bonds bonds)
The relative size of the electron cloud of two
The magnitude and number of non permanent-
molecules can be estimated by comparing molar
momentary polar sites increase as the size of the
masses, the structure of the molecules or the
electron cloud increases
location in the PT
The magnitude and number of non permanent-
momentary polar sites increase as the size of the
electron cloud increases
The energy required to separate molecules
The VDW interaction between molecules increases
increases as the number of non permanent polar
as the number of non permanent polar sites in the
sites in the molecules that interact to other similar
molecules increases
molecules increases
The VDW interaction between molecules increases The energy required to separate molecules
as the magnitude of non permanent polar sites in increases as the magnitude of non permanent polar
the molecules increases sites in the molecules that interact increase
States of Matter
In solids, molecules or ions may stick together in In solids, average electrostatic interactions between
In solids, particles vibrate in the ordered structure.
ordered structures-lattice molecules are strongest
In liquids particles move fast and collide in a
In liquids molecules or ions are disordered and In liquids average electrostatic interactions
disordered way while keeping constant contact
close to each other between molecules are weak
with each other (translation, rotation, vibration).
In gases, molecules are separated on average from each
In gases average electrostatic interactions between In gases, particles move very fast and collide with
other by distances that are large compared to the
molecules’ sizes
molecules are negligible each other.
During changes of state (melting, boiling,
Particles may stick together in large structures The energy required to boil a substance is equal to
condensation, freezing), or during dissolving, there
defined by their electrostatic interactions. the energy released when the substance condenses
are changes in the molecular mutual orientation
Boiling energy is higher than melting energy
While boiling all intermolecular bonds are broken, because while boiling all intermolecular bonds are
while melting only weakened and some broken. broken and while melting only weakened and some
broken
When a substance melts or boils, the amount of
energy transferred to the system is equal to the
energy required to separate the particles. Much
information can be obtained from melting and
boiling temperatures.
In many cases, an intramolecular bond (molecular The energy needed to break molecules into atoms
orbital) is stronger than an intermolecular bond is usually higher than their boiling energy
The different states of matter are determined by the
energy of the system
In a certain state of matter particles move faster
upon heating
Overview
Generally speaking, in a diatomic system bond Generally speaking, in a diatomic system, bonds
Generally speaking, in a diatomic system, bond
length can be mapped in a continuous scale from can be mapped on a continuous scale according to
energies decrease from ionic to polar covalent to
Van der Wals to non-polar covalent to polar the bond energy values that reflect the strength of
covalent to VDW for similar atomic radii bound
covalent to ionic for similar atomic radii bound the electrostatic forces from ionic to polar covalent
atoms
atoms to covalent bonds to Van der Waal's interactions
It is difficult to predict the relative strength of
electrostatic interaction (VDW and Hydrogen
bond) when molecules are very different. E.g.
ΣVDW interactions between molecules may be
stronger than ΣHB
There is a whole range of chemical bonds which There is a whole range of chemical bonds, which
we can map on a continuous scale according to the we can map on a continuous scale according to the
strength of the interaction bond energy bond values
Chemical bonds can be understood, among others, Chemical bonds can be understood, among others, Chemical bonds can be understood, among others,
by: attractive and repulsive forces, the equilibrium by: attractive and repulsive forces, the equilibrium by: attractive and repulsive forces, the equilibrium
point, the difference in EN values, the atomic EN point, the difference in EN values, the atomic EN point, the difference in EN values, the atomic EN
values, bond length and energy values, bond length and energy values bond length, and energy
Chemical bonds can be explained by quantum Chemical bonds can be explained by quantum
theory, but in practice, much can be qualitatively theory, but in practice, much can be qualitatively
explained without explicitly using this theory explained without explicitly using this theory
The magnitude of the electrostatic force between
two electric charges is inversely proportional to the
square of the distance between the two charges.
The magnitude of the electrostatic force between
two point electric charges is directly proportional
to the product of the magnitudes of each of the
charges