Chem Explorers

Unraveling the Secrets: Lewis Structures Octet Rules and Solubility Explained

The Magic of Lewis Structures and Octet Rules

As the world-leading expert in chemistry, you need to be familiar with different models in chemical bonding. One of the fundamental models that you’ll come across frequently is Lewis structures.

The Lewis structure is a diagram that illustrates the bonding between atoms in a molecule and the non-bonding valence electrons that reside in the molecule. To understand this model, we will first look at the structure of PF6 and the importance of valence electrons.

Lewis Structure, PF6, Bonding Electrons, Valence Electrons

Lewis Structure

The Lewis structure was developed by Gilbert Lewis, an American chemist who believed that chemical bonding could be explained by the interaction of valence electrons. The valence electrons are the outermost electrons in an atom and determine the reactivity of the element.

The Lewis structure model makes use of dots to represent valence electrons of elements. These dots are placed around the atomic symbol to represent the number of valence electrons in the atom.

Remember that the maximum number of valence electrons an element can have is limited to 8 electrons, which is the octet rule.


Let’s take a closer look at the PF6 molecule to see how it works. When we draw the Lewis dot structure of PF6, we see that there are six fluorine (F) atoms connected to a phosphorus (P) atom. The Lewis structure of PF6 indicates that each fluorine atom is connected to the phosphorus atom by a single bond, and the phosphorus atom carries a lone pair of electrons. There are also six nonbonding electrons, which are located on the fluorine atoms, evidenced by the dots around the fluorine symbol.

Bonding Electrons and Valence Electrons

Bonding electrons are the electrons that share in forming a bond between two elements. In a Lewis structure, bonding electrons are represented by lines between atoms in the diagram, showing how the atoms share electrons.

Meanwhile, valence electrons are the outermost electrons that determine how atoms react. In the PF6 example, there are twelve valence electrons surrounding the phosphorus atom, consisting of five electron pairs and two lone pairs. The five bonding pairs are formed between the phosphorus atom and fluorine atoms, while the lone pairs of electrons on the phosphorus atom are nonbonding.

Central Atom, Size, Electropositivity, and P

Central Atom

The central atom in a molecule is the atom that is attached to two or more other atoms in the molecule. The properties of this central atom determine the geometry of the molecule, making it an essential concept in molecular structure.


The size of an atom is an important factor that determines its bonding behavior. Atoms get larger as you move down a periodic table and get smaller as you move across it.

For instance, the size of a phosphorus atom increases when we move down Group 15, from nitrogen to bismuth.


Electropositivity is a measure of an elements tendency to donate electrons and form positive ions.

Phosphorus falls under the category of moderately electropositive elements, which is mostly due to its atomic size.

This electropositivity makes it easier for phosphorus to donate electrons to form covalent bonds with other elements like fluorine in the PF6 molecule.


Phosphorus is a non-metallic element in group 15 of the periodic table, and it has a total of five valence electrons. These five valence electrons are the building blocks of its chemical properties.

We have already seen how it plays a role in the PF6 molecule example. Additionally, these five valence electrons mean that it has space to form three more chemical bonds.

However, violating the octet rule by adding more than eight electrons to the outermost shell results in an unstable compound.

Octet Rule, Valence Orbital, P, and Violating Octet

Octet Rule

The octet rule is a fundamental concept in chemistry that determines whether or not an atom has an octet, or eight electrons in their outermost shell. Atoms tend to form ions or covalent bonds with other atoms in such a way that they can complete the octet rule, making themselves more stable.

Valence Orbitals

The valence orbital is the outermost shell of an atom. For instance, P has valence electrons in its third principal shell, which is a 3p orbital.

This valence electron shell determines the chemical properties of an element.

P and Violating Octet

Pouring an extra pair of electrons into valence shells violates the octet rule, making the compound less stable. For example, P is able to supply five electrons, but pouring another pair of electrons into the valence shell violates the octet rule.

Many compounds that violate octet are highly reactive, making them useful, for example in radical chemistry.

Hybridization, sp3d, d orbital, Bond Formation


Hybridization is the process of mixing and overlapping atomic orbitals to produce hybrid orbitals in order to create stable covalent bonds. These hybrid orbitals are different from the original atomic orbitals and are essential for explaining valence bond theory.

Sp3d Hybridization

Sp3d hybridization is a type of hybridization that involves mixing 3d, one s, and three p orbitals to form six sp3d hybrid orbitals. These orbitals form an octahedral structure around the central atom and can explain the stability of the PF6 molecule.

D Orbital

The d orbital holds up to ten electrons, just like the p orbital, but the d orbitals are located further from the nucleus and are capable of forming hybrid orbitals.

Bond Formation

Covalent bond formation is the process of sharing electrons between non-metallic elements to form a stable molecule. In the case of PF6, we see six fluorine atoms that bond covalently with phosphorus to form the hexafluorophosphate anion, which has a negative charge as a result of gaining one electron in the process.


Now you have a better understanding of Lewis structures and octet rules in chemical bonding. These models provide insight into how chemical compounds are formed, making them vital to recognize, understand and apply in the laboratory or workplace.

The properties of different elements determine their performance in bonding with other elements, making it important to know the elements in question before making any chemical decisions. We hope you have found this overview of these models useful.

Valence Electrons and Bond Formation

Valence Electrons, Outermost Orbital, Bond Formation

Valence Electrons

In chemistry, valence electrons are outer electrons in an atom. In simpler terms, valence electrons are those electrons in the outermost orbital that are involved in chemical reactions.

It is essential to understand valence electrons when analyzing chemical reactions.

Outermost Orbital

The outermost orbital is the highest energy level that contains electrons. It is known as the valence shell.

The number of electrons in the valence shell is an essential factor in determining an elements chemical behavior.

Bond Formation

Bond formation is a result of the interactions between valence electrons of two different atoms. These electrons distribute their energy to form a chemical bond.

The valence electrons are mainly responsible for an atoms ability to bond with other atoms.

Valence Electrons in PF6 Molecule


The PF6 molecule is a negative ion consisting of one phosphorus (P) atom and six fluorine (F) atoms. Each of the F atoms forms a covalent bond with the P atom.

These bonds are formed through the sharing of electrons between the fluorine atom and the phosphorus atom.

Valence Electrons in PF6

In the PF6 molecule, the phosphorus atom has five valence electrons, while each fluorine atom contributes seven valence electrons, resulting in a total of 42 valence electrons. When we add the lone pair located on the central phosphorus atom, we get a total of 48 valence electrons.

The result is an octahedral complex as the six fluorine atoms will occupy the edges of a cube, with the P atom at the center of the cube.

Bond Formation in PF6

The formation of the PF6 molecule involves the phosphorus atom sharing one of its five valence electrons with each of the six fluorine atoms to form covalent bonds. The result is a molecule with negative charge because of the extra electron added during the ionization process.

The extra electron makes it easy for the PF6 molecule to form bonds with other elements that require an electron pair for bonding.

Octet Rules in Bond Formation

Octet, Valence Orbital, Bond Formation, Octet Rule


The octet rule is a concept describing the importance of having eight electrons in the outermost of an atom for it to be stable. The rule states that elements will work to achieve a full octet of electrons in their valence shell by either gaining or sharing electrons with other elements.

Valence Orbital

The valence orbital is the outermost energy level of an atom, containing electrons that are involved in chemical bonding. The number of electrons in the valence shell determines the chemical behavior of the atom.

Bond Formation

Bond formation occurs when atoms share or transfer electrons to form stable compounds. Atoms bond in such a way as to complete the octet in their outermost shell.

Octet Rule

The octet rule is an essential concept in chemistry, as it determines the chemical behavior of elements and how they react with each other. For most non-metallic elements, the rule states that they will combine with other elements in such a way as to have eight electrons in their valence shell to achieve stability.

Expanding Octet

The octet rule applies mainly to elements such as carbon, nitrogen, and oxygen. However, the rule does not explain the bonding of some elements like sulfur and phosphorus.

These elements are capable of forming stable compounds with more than eight electrons in their valence shell, an exception called the expanding octet or the extended octet.

Violation of Octet

The violation of the octet rule is characterized by elements that have more than eight electrons in their outermost shells.

These elements are often found in the third and higher periods of the periodic table and usually include transition metals d and f orbitals.

56 Electrons

Among the elements known for violating the octet rule are elements from the third and higher periods of the periodic table, including the transition metals d and f orbitals. A perfect example is the hexachlorotellurate (TeCl6) molecule, consisting of seven elements and 56 electrons, with the tellurium atom having 12 electrons, more than eight in its valence shell.


In conclusion, understanding the importance of valence electrons, octet rules, and bond formation concepts is crucial to comprehend chemical reactions fully. The valence electrons are responsible for atom bonding, while the octet rule describes how elements bond to achieve stability.

Violating the octet is possible by expanding the octet, and elements from the third and higher periods usually do this. As a chemistry expert, understanding these concepts will help you to have a better grip on chemical bonding and reactions.

Lone Pairs in Chemical Bonding

Lone Pairs, Non-Bonded Electrons, F, P

Lone Pairs

Lone pairs are pairs of valence electrons that do not participate in chemical bonding. They are also known as non-bonded electrons.

Lone pairs are essential in understanding the shape and reactivity of molecules.

F and P Lone Pairs

In the PF6 molecule, each fluorine (F) atom forms a single bond with the phosphorus (P) atom. These bonding pairs of electrons are involved in forming the covalent bonds.

However, the P atom also possesses lone pairs of electrons. In the case of PF6, there are two lone pairs of electrons on the P atom.

Lone Pairs, Valence Electrons, F, PF6

Lone Pairs in PF6

The PF6 molecule has a phosphorus (P) atom at its center, surrounded by six fluorine (F) atoms. The P atom has a total of five valence electrons.

When we consider the lone pairs, we note that the P atom also possesses two lone pairs of electrons. In the Lewis structure of PF6, the two lone pairs of electrons are represented as dots around the P atom.

Valence Electrons and Lone Pairs

The presence of lone pairs affects the geometry of a molecule. Lone pairs are usually more repulsive than bonded pairs, pushing other atoms away from them.

They can also affect the molecule’s polarity and reactivity.

Molecular Shape and Geometry

Molecular Shape, Octahedral, Central Atom, Geometry

Molecular Shape

Molecular shape refers to the three-dimensional arrangement of atoms in a molecule. It is influenced by the bonding and lone pairs of electrons surrounding the central atom.


An octahedral shape is a type of molecular shape in which the central atom is surrounded by six atoms or groups of atoms arranged in a symmetrical manner. The arrangement resembles a three-dimensional octahedron, a shape with eight faces.

Central Atom

The central atom is the atom in a molecule that is bonded to two or more other atoms. In the case of an octahedral shape, the central atom is connected to six other atoms or groups of atoms.


Geometry refers to the spatial arrangement of atoms in a molecule based on the bond angles and lone pairs of electrons. It describes the relative positions of the atoms in the molecule.

AX6, VSEPR Theory, Octahedral Geometry, No Lone Pairs


In the context of molecular geometry, AX6 refers to a molecular formula in which the central atom is bonded to six other atoms, with no lone pairs of electrons. The “A” represents the central atom, and the “X” represents the surrounding atoms or groups of atoms.

VSEPR Theory

The VSEPR (Valence Shell Electron Pair Repulsion) theory is a model used to predict the geometry of molecules based on the repulsion between electron pairs. According to the VSEPR theory, electron pairs, whether bonding or non-bonding, will arrange themselves in a way to minimize repulsion.

Octahedral Geometry

Octahedral geometry is a molecular shape in which the central atom is surrounded by six other atoms or groups of atoms, forming an octahedron. This shape is often observed in molecules with AX6 electron pair arrangements, where there are no lone pairs around the central atom.

No Lone Pairs in Octahedral Geometry

In an octahedral molecule with AX6 electron pair arrangements, there are no lone pairs of electrons around the central atom. All six bonding pairs surround the central atom in a symmetrical manner, resulting in an octahedral molecular shape.


Understanding the role of lone pairs and the concept of molecular shape and geometry is essential in comprehending the behavior and properties of chemical compounds. Lone pairs influence the reactivity and shape of molecules.

Octahedral geometry, with no lone pairs, is observed in molecules with AX6 electron pair arrangements. The VSEPR theory provides a valuable framework for predicting molecular shapes based on the repulsion between electron pairs.

By delving into these topics, you will gain a deeper understanding of the fascinating world of chemical bonding and the three-dimensional arrangement of atoms in molecules.

Bond Angles in Octahedral Molecules

Bond Angle, F-P-F, Octahedral Molecule, Perfect 90

Bond Angle

The bond angle refers to the angle formed between two adjacent bonds in a molecule. It provides information about the spatial arrangement of atoms in a molecule.

F-P-F Bond Angle in Octahedral Molecules

In an octahedral molecule such as PF6, the bond angle between two adjacent fluorine (F) atoms connected to the central phosphorus (P) atom is approximately 90 degrees. This angle arises from the repulsion between the bonding pairs of electrons and gives the molecule its symmetrical structure.

Perfect 90 Degree Bond Angle

In an ideal octahedral molecule, the bond angles between adjacent atoms would be precisely 90 degrees. However, due to various factors like lone pairs and molecular distortion, the actual bond angle might deviate slightly from the perfect 90 degrees.

Bond Angle Formula, Hybridization Value, Bents Rule, 90

Bond Angle Formula

Determining bond angles in a molecule can be done using the VSEPR theory and the formula for bond angles. The formula is:

Bond Angle = 180 – (360 / n)

Where “n” represents the number of surrounding atoms or groups of atoms.

Hybridization Value and Bond Angles

Hybridization is a concept that explains the bonding and molecular geometry of atoms. The hybridization value of an atom indicates the number of orbitals involved in bonding.

In an octahedral molecule like PF6, the central phosphorus atom has an sp3d2 hybridization value, which corresponds to six hybrid orbitals. Each hybrid orbital forms a sigma bond with a fluorine atom, resulting in an octahedral geometry.

Bent’s Rule and Bond Angles

Bent’s rule states that in molecules with central atoms having two different substituents, the more electronegative substituents will preferentially occupy the axial positions. This arrangement affects the bond angles in the molecule, leading to deviations from the ideal 90-degree angle.

However, in the case of PF6, where all the substituents are the same (F), Bent’s rule is not applicable, and the bond angles remain close to 90 degrees.

Formal Charge in Molecules

Formal Charge, Charge Present, Molecule, Atom

Formal Charge

Formal charge is a concept used to determine the distribution of electrons in a molecule. It helps in evaluating the stability of a molecule and understanding the charge distribution on atoms.

Charge Present in a Molecule

In a molecule, charge can be present on specific atoms, resulting from the gain or loss of electrons. Formal charge helps in identifying the distribution of charge within the molecule.

Formal Charge Calculation, P, F, PF6

Formal Charge Calculation

Formal charge is calculated using the formula:

Formal Charge = (Number of Valence Electrons) – (Number of Lone Pair Electrons + 0.5 * Number of Bonding Electrons)

Calculating Formal Charge in PF6

In the case of the PF6 molecule, the phosphorus (P) atom has a formal charge of 0. The formal charge calculation for P is as follows:

Formal Charge on P

Formal Charge on P = (Number of Valence Electrons on P) – (Number of Lone Pair Electrons on P + 0.5 * Number of Bonding Electrons on P)

Since P has five valence electrons, no lone pairs, and six bonding electrons (since it forms six sigma bonds with F), the formal charge on P is 0.

Calculation for F

For the fluorine (F) atoms in PF6, each atom has a formal charge of -1. The calculation is as follows:

Formal Charge on F = (Number of Valence Electrons on F) – (Number of Lone Pair Electrons on F + 0.5 * Number of Bonding Electrons on F)

Since F has seven valence electrons, no lone pairs, and one bonding electron (forming one sigma bond with P), the formal charge on F is -1.


Understanding bond angles, formal charge, and charge distribution in molecules provides vital insights into the structure, stability, and reactivity of chemical compounds. In octahedral molecules like PF6, the bond angles between adjacent atoms are close to 90 degrees, although variations may occur due to factors such as lone pairs and molecular distortion. Formal charge calculations offer a method to assess the distribution of electrons and charge within a molecule, providing valuable information for analyzing molecular behavior.

By delving into these topics, you will enhance your understanding of chemical bonding and the intricacies of molecular structure and properties.

Polar and Nonpolar Molecules

Polar, Nonpolar, Permanent Dipole Moment, Cancellation

Polar and Nonpolar Molecules

In chemistry, molecules can be classified as polar or nonpolar, depending on the distribution of their electrons and the presence of a dipole moment. These classifications are important in understanding the physical and chemical properties of molecules.

Permanent Dipole Moment

A permanent dipole moment is a measure of the separation of positive and negative charges within a molecule. It occurs when there is an uneven distribution of electron density, resulting in a partial positive charge on one end of the molecule and a partial negative charge on the other end.

Cancellation of Dipole Moment

In some molecules, the individual dipole moments of the bonds can cancel each other out, resulting in a molecule with no overall dipole moment. This cancellation can occur when the molecular structure has symmetry, and the bond dipoles are equal and opposite in direction.

Symmetrical Molecules, Equal and Opposite Dipole Moment, Nonpolar

Symmetrical Molecules

Symmetrical molecules are those that possess an arrangement of atoms or groups of atoms that exhibit symmetry. In these molecules, the atoms or groups of atoms are distributed evenly in space.

Equal and Opposite Dipole Moment

In symmetrical molecules, the individual bond dipole moments are equal in magnitude but opposite in direction. This means that the partial positive and negative charges on each bond cancel each other out, resulting in a molecule with no net dipole moment.

Nonpolar Molecules

Molecules with no net dipole moment are classified as nonpolar molecules. These molecules have equal sharing of electrons and exhibit symmetrical charge distributions.

Solubility and Electrolytes

Electrolyte, Soluble in Water, Ionized, Electricity


An electrolyte is a substance that, when dissolved in water or melted, forms a solution that conducts electricity.

Electrolytes can exist in the form of ions, which are atoms or groups of atoms that have gained or lost electrons, resulting in a net electric charge.

Soluble in Water

The solubility of a substance refers to its ability to dissolve in a particular solvent, such as water. Some substances are highly soluble in water, meaning they can readily dissolve and form a homogenous solution with water.


When an electrolyte dissolves in water, it undergoes a process called ionization, where the compound breaks up into its constituent ions. The ions can freely move in the water, allowing the solution to conduct electricity.

Electricity in Electrolyte Solutions

The presence of ions in electrolyte solutions allows the flow of electric current. When a potential difference is applied across the solution, the ions move towards the opposite charges, facilitating the flow of electricity.

Dissolved in Water, Hydrolysis, Solubility, PF6, Water

Dissolved in Water

When a substance is dissolved in water, the solute particles become dispersed throughout the solvent, resulting in a homogenous mixture. This process involves the breaking of intermolecular forces in the solute and the formation of new solute-solvent interactions.


Hydrolysis is a chemical process in which a compound reacts with water, resulting in the breaking of bonds within the compound. This process can occur when certain substances dissolve in water, leading to the formation of new compounds or ions.

Solubility of PF6 in Water

The solubility of a substance like PF6 in water depends on the nature of the interactions between the solute and solvent particles.

PF6 is a negatively charged ion, and water is a polar molecule. Since PF6 and water have opposite charges, they can interact through ion-dipole interactions, leading to the solubility of PF6 in water.

Water as a Solvent

Water is often called the “universal solvent” because it can dissolve a wide range of substances. This exceptional solubility arises from the ability of water molecules to form strong hydrogen bonds, allowing them to interact with other polar or charged molecules.


Understanding the concepts of polar and nonpolar molecules, dipole moments, and solubility in electrolyte solutions provides valuable insights into the behavior and properties of chemical compounds.

Polar molecules possess a permanent dipole moment, while nonpolar molecules have canceling dipole moments.

Electrolytes are substances that can conduct electricity when dissolved in water, forming ions through ionization. The solubility of a substance in water depends on the nature of its interaction with the water molecules.

Water’s unique properties as a solvent make it capable of dissolving a wide range of substances and facilitating important chemical processes such as hydrolysis. By exploring these topics, you deepen your knowledge of chemical interactions and their impact on solubility and conductivity.

Solubility in Water

Soluble in Water, H-Bonding, Size, Electronegativity

Soluble in Water

Solubility in water refers to the ability of a substance to dissolve in water. Some substances readily dissolve in water, resulting in a homogenous mixture, while others have limited solubility or are insoluble.

H-Bonding and Solubility

Hydrogen bonding plays a crucial role in determining the solubility of certain compounds in water. Hydrogen bonds form between the hydrogen atom of one water molecule and the electronegative atom (such as oxygen or nitrogen) of another molecule.

Size and Solubility

The size of a molecule can affect its solubility in water. Smaller molecules are generally more soluble because they can fit between water molecules and form stronger intermolecular interactions.

Electronegativity and Solubility

The electronegativity of a substance affects its solubility in water. Generally, substances with higher electronegativity, which can form stronger hydrogen bonds with water, are more soluble in water.

Hydrophobic, Low Solubility, PF6, Water

Hydrophobic Substances

Hydrophobic substances are molecules that do not readily dissolve in water. They typically have nonpolar bonds and are repelled by water molecules, ultimately leading to low solubility.

Low Solubility of PF6 in Water

PF6, or hexafluorophosphate, is a hydrophobic and nonpolar ion. The fluorine atoms surrounding the central phosphorus atom in PF6 result in a molecule with a symmetrical charge distribution, leading to low solubility in water.

Covalent and Ionic Bonds

Covalent, Ionic, Fajans Rule, Polarizability

Covalent and Ionic Bonds

Covalent bonds are formed when two atoms share electrons. In contrast, ionic bonds occur when one atom transfers electrons to another, resulting in the formation of oppositely charged ions.

Fajans Rule

Fajans rule states that for a compound to exhibit predominantly covalent character, there should be small differences in electronegativity between the atoms involved, as well as large size and polarizability of the cation.


Polarizability refers to how easily the electron cloud of an atom or ion can be distorted by an external electric field. Larger and more loosely held electron clouds are more polarizable.

Sharing of Electrons, Polar Bond, Hybridization, PF6

Sharing of Electrons

In covalent bonds, atoms share electrons in order to achieve a stable electron configuration. The sharing of electrons allows the atoms to fill their respective valence shells, resulting in a more stable compound.

Polar Bond

A polar bond is a covalent bond in which there is an unequal sharing of electrons due to differences in electronegativity between the bonded atoms. The more electronegative atom attracts the shared electrons closer to itself, resulting in a partial positive charge on one atom and a partial negative charge on the other.


Hybridization is a concept that describes the mixing of atomic orbitals to form new hybrid orbitals that are involved in bonding. It helps explain the geometry and properties of covalent compounds.

PF6 and Bonding

In the PF6 ion, phosphorus (P) forms covalent bonds with six fluorine (F) atoms. The P atom undergoes sp3d2 hybridization to form the six sigma bonds with the F atoms.

The nonpolar nature of the PF6 ion is a result of the symmetr

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