THE MATRIX
The charged particles
Protons are positive
Electrons are negative
Nuclei are positive
The charge of the nucleus equals the number of protons
In a neutral atom the number of electrons equals the number of protons
If the number of electrons differs the number of protons, the atom is charged and it is called a ion
Positive ions have fewer electrons than protons,
Negative ions have more electrons than protons
Momentary partial charges (δ- and δ+) in the electron cloud are caused because electrons have no fixed position
Momentary partial charges (δ- and δ+ ) in the electron cloud are caused due to momentary asymmetric changes in the distribution of the electrons
There are two types of electrostatic interactions: attraction and repulsion
The charged particles
Protons are positive
Electrons are negative
Nuclei are positive
The charge of the nucleus is defined by the number of protons
In a neutral atom the number of electrons equals the number of protons
Nanostructure - electron population technique
In each energy level there is a specific number of orbitals
Each orbital is populated by 1 or 2 electrons at the most
Lower energy levels get filled before higher ones
Empty orbitals get filled before partially populated orbitals in the same energy level
The maximum number of electrons in the first energy level is 2, in the second energy level is 8, in the third energy level is 8 (till atomic number 18)
If the number of electrons differs the number of protons, the atom is charged and it is called a ion
Positive ions have fewer electrons than protons,
Negative ions have more electrons than protons
Momentary partial charges (δ- and δ+) in the electron cloud are caused because electrons have no fixed position
Momentary partial charges (δ- and δ+ ) in the electron cloud are caused due to momentary asymmetric changes in the distribution of the electrons
Energy levels in the atom
Electrons are found around the nucleus in energy levels
The distance of an electron from the nucleus
is determined by its energy
In average, electron populating lower energy levels are closer to the nucleus than those populating higher energy levels
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
Nuclei consist of protons and neutrons
Description of interactions
Atoms consist of nuclei and electrons
Electrons move around the nucleus
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 the nucleus (Bohr’s model)
The valence electrons are the electrons in the outer populated energy level
Atoms are mostly vacuum
Electrons have no fixed position in the atom, but can be found everywhere in the electron cloud (a region) at once
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
Periodic Table (PT)
There is an electrical attraction between the nucleus and electrons
There is an electrical repulsion between the electrons
Bohr's model doesn't explain why electrons don't stick to the nuclei
The attraction between the nucleus and electrons hold the atom together
Momentary partial charges (δ- and δ+ ) in the electron cloud are possible because electrons have no fixed position and repel each other
Magnitude of interaction between nuclei and electrons (Coulomb's law)
Ionization energy
Energy is needed to separate an electron from its atom (ionization energy)
The ionization energy increases as the attraction force between the nucleus and the electron increases
The Periodic Table (PT) & ionization energy

The number of valence electrons equals the group number in the PT
Coulomb's law (declarative, operational and high)
The number of populated energy levels equals the row number in the PT
The atomic number equals the number of protons
The attraction force between a nucleus and an electron increases as the number of energy level in which the electron is decreases
The attraction force between a nucleus and an electron increases as the distance between them decreases
The attraction force between a nucleus and an external level electron increases as the atomic number increases among particles of similar size.
The attraction force between nucleus and external level electron increases as nucleus charge increases among particles of similar size.
The general trend is that the size of an atom decreases along the PT row
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
PT row due to the increase in attraction force 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
The bound atom's characteristics
The number of protons doesn't change in chemical reactions.
Atoms of different elements have a different number of protons and electrons which influences their chemical activity
Electronegativity (EN)
EN reflects the relative attraction between the bonding electrons and the rest of the atom
Atoms may form a single bond, a double bond, or a EN is influenced among other, by the energy of
Ionization energy of a valence electron decreases as the number of populated energy levels increases
(along a column of the PT)
Ionization energy decreases along a column in the
PT as the distance between the nucleus and valence electrons increases
Along a row in the PT, the general trend is that ionization energy increases as the nucleus charge increases
When comparing the ionization energy of similar size atoms (radius), the general trend is that the ionization energy of the valence electron occupying the same energy level increases as the nucleus charge increases

triple bond.
An atom's valence electrons determine the number of bonds an atom can form (in organic molecules) according to the octet rule
General characteristics of the bond nanostructure ionization and the electron affinity
The EN of an atom is influenced by the adjacent bound atoms
The bonding electrons are paired
The bonding electrons are shared forming a molecular orbital.
A molecular orbital represents the probability to find electrons in the space around the bound atoms
Description of interactions (general)
There is an electrical attraction force between bonding electrons and the nuclei of the bound atoms
There is an electrical repulsion force between the non-bonding electrons of the bound atoms
There is an electrical repulsion force between the nuclei of the bound atoms
There is an electrical repulsion force between bonding electrons
There is mostly vacuum between nuclei in a bond
Empty molecular orbitals get filled before partially populated orbitals in the same energy level
The bond length is the distance between nuclei at which the atoms are in equilibrium
When two atoms move toward each other their orbitals overlap with each other forming a molecular orbital
When the bond is broken, the atoms are separated and the molecule is broken
The interaction between two atoms vs distance between two nuclei (Coulomb's law)
At the bond length there is an equilibrium state because attraction forces are equal to repulsion forces between the bound atoms
Two atoms move toward each other because the attraction forces are stronger than the repulsion forces between them
At a closer distance than the bond length atoms move away from each other because, repulsion forces are stronger than attraction forces between them
When the atoms are far from each other, any interaction- attraction or repulsion is negligible.
Description of the energy involved (general)
Energy is required to break a bond between atoms
The energy required to break a chemical bond, to separate the 2 atoms is the Bond energy
The energy required to break a bond into atoms is equal to the energy released when the bond is formed
When 2 bound atoms are at bond length the system is at minimum energy
Two atoms bond if the energy of the bound atoms is lower than that of the two separated atoms
When 2 bound atoms are at bond length, energy is required to separate or get the atoms closer to each other
When the atoms are far from each other, the energy of the system is given by the sum of the energy of both atoms.

Types of chemical bonds - EN & electron distribution
Thumb rule:
Non-metals form covalent bonds between themselves, Metals form ionic bonds with nonmetals
Electric forces between electrons and nucleus hold bound atoms together at the bond length.
Types of chemical bonds - EN & charge distribution
In general, the EN of nonmetal atoms is higher than the EN of metal atoms
Atoms with same EN form covalent (non polar) bonds
In covalent (non polar) bonds the probability of finding bonding electrons around both atoms is equal
Atoms with similar but not identical EN form polar covalent bonds
In polar covalent bonds the more EN atom is partially negatively charged δ- and the less EN atom bound to it is partially positively charged δ+
The probability of finding bonding electrons around the more EN atom is greater
In intramolecular bonds electrons are transferred or shared in molecular orbitals
Atoms with very different EN form ions, a negative nonmetal ion, a positive metal ion
In ionic bonds the more EN atom is a negative ion, the less EN atom is a positive ion.
Bond length

bond strength, bond energy
There are permanent partial charges (δ- and δ+ ) in the electron cloud due to the asymmetric distribution of the electrons.
In covalent (non polar) bonds the bonding electrons are equally shared because both atoms have the same EN
In a Polar covalent bond, the electrons are not evenly shared; in average, the electrons are more attracted to the more electronegative atom
In polar covalent bonds the more EN atom is partially negatively charged δ- and the less EN atom bound to it is partially positively charged δ+
The polarity of the bond increases as the difference in the EN of the bound atoms increases
Permanent partial charges are created due to the asymmetric distribution of electrons in chemical bonds.
In Ionic bonds negative nonmetal ions and positive metal ions can be assumed to exist since in bonds between atoms with very different EN bonding electrons are not shared, but are mostly by the electronegative atom
Ionic bonds are extreme cases of polar bonds. The more electronegative atom is negatively charged (-) and the less electronegative atom bound to it is positively charged (+)
Magnitude of interaction (Coulomb's law ) Bond energy

bond strength, bond length

In general, bond length decreases as the strength of a bond and bond energy increase
Bond length increases with increasing radius of the bound atoms
Bond length increases as the total attractive and repulsive forces decrease
Bond length increases from triple to double to single bond (for the same atoms)
For similar size bound atoms, bond length increases as the number of lone pairs decreases
For similar size bound atoms, bond length increases as the difference in EN decreases
Nanostructure
Once paired in a covalent bond electrons 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 number of electrons required to complete its valence energy level by sharing, transferring or receiving electrons (octet rule)
The strength of a bond increases as the bond energy increases
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 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 strength) increase with decreasing radius of the bound atoms
The total attractive (and repulsive) forces (the bond strength) increase as the distance between the bonding electrons and nuclei decreases
The strength of a bond increases from single to double to triple (for the same atoms)
The total attractive (and repulsive) forces increases as the number of bonding electrons between two bound atoms increases
For similar size bound atoms, the strength of a bond 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
Once paired in a covalent bond bonding electrons cannot take part in additional covalent bonds
In general, bond energy increases as the bond length decreases
The bond energy represents the bond strength
Bond energy increases with decreasing radius of the bound atoms
Bond energy increases with increasing attractive and repulsive forces
The bond energy increases from single to double to triple
For similar size atoms, the bond energy increases as the difference in EN increases
Atoms can form a molecule if the energy of the bound atoms (molecule) is lower than the sum of the energies of the separated atoms

In ionic bonds, the ions’ energy levels can be approximated as full and can be deduced by the PT
Shape
The basic building block of a substance is neutral
Atoms bond into well defined shaped molecules The shape of a molecule is defined by electric forces
In ionic bonds, the ions’ energy levels can be approximated as full and can be deduced by the PT
Molecules are not "rigid"
The shape and size of a molecule are defined by the size and shape of its electron cloud
The shape of the molecule is determined by the
VSEPR theory (repulsion of electron cloudsorbitals)
The molecule’s geometrical structure is such that it is at minimum energy
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 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,
The polarity of the molecule is determined by the polarity of its bonds, its shape and its symmetry
Nanostructure
Interactions in nanostructure
In covalent, metallic and ionic solids molecular
"building blocks" cannot be identified
In an ionic lattice, ions are ordered in a positive – negative pattern
Charged particles (charge distribution)
In a covalent lattice atoms are covalently bound
In an ionic lattice, ions are ordered in a positive – negative pattern due to electrostatic interaction.
Charged particles (charge distribution)
Covalent lattices are solids at room temperature because the thermal energy available at room temperature is not enough to break the covalent bond
Most ionic substances are solids because the thermal energy available at room temperature is not 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

In metal lattices, bonding electrons are delocalized over ordered atoms (or ions).
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
Description of the bound particles
Van der Waal's forces are electrostatic interactions between polar molecules , non polar molecules or between individual atoms
In a hydrogen bond the "exposed” hydrogen atom binds to a lone pair of an EN atom which is not covalently bound to it (H
δ+ δ:
X-H
δ+
)
Hydrogen bonds have a linear geometry H :X-H
Van der Waal's forces are electrostatic interactions between polar molecules, non polar molecules or between individual atoms
The delocalization of electrons in metals is due to the presence of conducting bands (overlapping orbitals)
Interactions between bound particles
Van der Waal's forces are electrostatic interactions between molecules or individual atoms, caused by momentary or permanent polarization of 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 binds to a lone pair of an EN atom which is not covalently bound to it (H
δ+ δ:
X-H
δ+
)
Hydrogen bonds have H X-H 180 o
– a linear geometry which cannot be explained only by electrostatic interactions
Van der Waal's forces are electrostatic interactions between molecules or individual atoms, caused by momentary or permanent polarization of molecules (δ- and δ+).
The shape, polarity and functional groups of the molecule determine the interactions between

In molecular substances the molecular "building blocks" can be identified in all states of matter 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, hydrogen bonds or other electrostatic interactions.
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 number of non bonding electron pairs on the electro-negative atom X per molecule (acceptor)
The number of "exposed" H atoms per molecule.
(donor)
The electrostatic interaction (VDW and Hydrogen bonds) between molecules increases as the number of permanent polar sites in the molecules that are bound increases.
The energy required to separate molecules increases with the number of permanent polar sites in the molecules (e.g.,the number of Hydrogen bonds per molecule)
The relative size of the electron cloud of two molecules can be estimated by comparing molar masses, the structure of the molecules or the location in the PT
The electrostatic interaction (VDW and Hydrogen bond) between molecules increases as the magnitude of the permanent polar sites in the molecules that are bound increase. E.g. A larger dipole moment is formed in OH than in NH bonds
The energy required to separate molecules increases as the magnitude of permanent polar sites in the molecules that interact increase. (e.g. A larger dipole moment is formed in OH than in NH bonds)
The magnitude and number of non permanent- momentary polar sites increase as the size of the electron cloud increases
The magnitude and number of non permanent- momentary polar sites increase as the size of the electron cloud increases
The VDW interaction between molecules increases as the number of non permanent polar sites in the molecules increases
The VDW interaction between molecules increases as the magnitude of non the molecules increases permanent polar sites in
The energy required to separate molecules increases as the number of non permanent polar sites in the molecules that interact to other similar molecules increases
The energy required to separate molecules increases as the magnitude of non permanent polar sites in the molecules that interact increase

In solids, molecules or ions may stick together in ordered structures-lattice
In liquids molecules or ions are disordered and close to each other
In gases, molecules are separated on average from each other by distances that are large compared to the molecules’ sizes
During changes of state (melting, boiling, condensation, freezing), or during dissolving, there are changes in the molecular mutual orientation
In solids, average electrostatic interactions between molecules are strongest
In liquids average electrostatic interactions between molecules are weak
In gases average electrostatic interactions between molecules are negligible
Particles may stick together in large structures defined by their electrostatic interactions.
In solids, particles vibrate in the ordered structure.
In liquids particles move fast and collide in a disordered way while keeping constant contact with each other (translation, rotation, vibration).
In gases, particles move very fast and collide with each other.
While boiling all intermolecular bonds are broken, while melting only weakened and some broken.
In many cases, an intramolecular bond (molecular orbital) is stronger than an intermolecular bond
The energy required to boil a substance is equal to the energy released when the substance condenses
Boiling energy is higher than melting energy because while boiling all intermolecular bonds are 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.
The energy needed to break molecules into atoms 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
Generally speaking, in a diatomic system bond length can be mapped in a continuous scale from
Van der Wals to non-polar covalent to polar covalent to ionic for similar atomic radii bound atoms
Generally speaking, in a diatomic system, bonds can be mapped on a continuous scale according to the bond energy values that reflect the strength of the electrostatic forces from ionic to polar covalent 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.
Generally speaking, in a diatomic system, bond energies decrease from ionic to polar covalent to covalent to VDW for similar atomic radii bound atoms

Chemical bonds can be understood, among others, by: attractive and repulsive forces, the equilibrium point, the difference in EN values, the atomic EN values, bond length and energy
ΣVDW interactions between molecules may be stronger than ΣHB
There is a whole range of chemical bonds which we can map on a continuous scale according to the strength of the interaction
Chemical bonds can be understood, among others, by: attractive and repulsive forces, the equilibrium point, the difference in EN values, the atomic EN values, bond length and energy
Chemical bonds can be explained by quantum theory, but in practice, much can be qualitatively 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
There is a whole range of chemical bonds, which we can map on a continuous scale according to the bond energy bond values
Chemical bonds can be understood, among others, by: attractive and repulsive forces, the equilibrium point, the difference in EN values, the atomic EN values bond length, and energy
Chemical bonds can be explained by quantum theory, but in practice, much can be qualitatively explained without explicitly using this theory