Chemical Bonds

Definitions of Chemical Bonds;

A chemical bond is an attraction between atoms that allows the formation of chemical substances that contain two or more atoms.

 The bond is caused by the electrostatic force of attraction between opposite charges, either between electrons and nuclei, or as the result of a dipole attraction.

The strength of chemical bonds varies considerably; there are "strong bonds" such as covalent or ionic bonds and "weak bonds" such as dipole–dipole interactions, the London dispersion force and hydrogen bonding.

Gilbert Newton Lewis ForMemRS(October 23, 1875 – March 23, 1946)was an American physical chemist known for the discovery of the covalent bond and his concept of electron pairs; his Lewis dot structures and other contributions to valence bond theory have shaped modern theories of chemical bonding.

Lewis has successfully contributed to thermodynamics, photochemistry, and isotope separation, and is also known for his concept of acids and bases.

Examples of Lewis dot-style chemical bonds between carbon (C), hydrogen (H), and oxygen (O). Lewis dot depictures represent an early attempt to describe chemical bonding and are still widely used today.

Lewis Successfully Contributed to:

Thermodynamics Photochemistry Isotope separation And also known for

his concept of acids and bases.

Thermodynamics

Is a branch of natural science concerned with heat and its relation to energy and work.

It defines macroscopic variables (such as temperature, internal energy, entropy, and pressure) that characterize materials and radiation, and explains how they are related and by what laws they change with time. 

Thermodynamics describes the average behavior of very large numbers of microscopic constituents, and its laws can be derived from statistical mechanics.

Annotated color version of the original 1824 Carnot heat engine showing the hot body (boiler), working body (system, steam), and cold body (water), the letters labeled according to the stopping points in Carnot cycle.

The classical Carnot heat engine

Photochemistry A sub-discipline of

chemistry, is the study of chemical reactions that proceed with the absorption of light by atoms or molecules. Everyday examples include photosynthesis, the degradation of plastics and the formation of Vitamin D with sunlight.

Isotope Separation

Is the process of concentrating specific isotopes of a chemical element by removing other isotopes, for example separating natural uranium into enriched uranium and depleted uranium. 

This is a crucial process in the manufacture of uranium fuel for nuclear power stations, and is also required for the creation of uranium based nuclear weapons.

Plutonium-based weapons use plutonium produced in a nuclear reactor, which must be operated in such a way as to produce plutonium already of suitable isotopic mix or grade. 

While different chemical elements can be purified through chemical processes, isotopes of the same element have nearly identical chemical properties, which makes this type of separation impractical, except for separation of deuterium.

A cascade of gas centrifuges at a U.S. uranium enrichment plant.

Schematic diagram of uranium isotope separation in a Calutron.

Lewis acids and bases

The term Lewis acid refers to a definition of acid published by Gilbert N. Lewis in 1923, specifically: 

An acid substance is one which can employ an electron lone pair from another molecule in completing the stable group of one of its own atoms.

The modern-day definition of Lewis acid, as given by IUPAC is a molecular entity (and the corresponding chemical species) that is an electron-pair acceptor and therefore able to react with a Lewis base to form a Lewis adduct, by sharing the electron pair furnished by the Lewis base.

This definition is both more general and more specific—the electron pair need not be a lone pair (it could be the pair of electrons in a π bond, for example), but the reaction should give an adduct (and not just be a displacement reaction).

A Lewis base, then, is any species that donates a pair of electrons to a Lewis acid to form a Lewis adduct. For example, OH− and NH3 are Lewis bases, because they can donate a lone pair of electrons.

Diagram of Lewis acids and bases

Diagram of Lewis acid and base bond types. For example, an s-LUMO Lewis acid such as the sodium ion (Na+), interacts with a Lobe-HOMO Lewis base such as the hydroxide ion (OH–), to give sodium hydroxide, a Type 7 complex.

Types of Chemical Bonds:

Ionic Bonds/ Ionic Bonding

Covalent Bonds/ Covalent Bonding

Ionic Bonds/ Ionic Bonding

Is a type of chemical bonding that involves the electrostatic attraction between oppositely charged ions. These ions represent atoms that have lost one or more electron (known as cations) and atoms that have gained one or more electrons (known as an anions).

In the simplest case, the cation is a metal atom and the anion is a nonmetal atom, but these ions can be of a more complex nature.

Are formed when metallic and non metallic atoms interact to form a bond.

It is important to recognize that clean ionic bonding - in which one atom "steals" an electron from another - cannot exist: All ionic compounds have some degree of covalent bonding, or electron sharing.

Thus, the term "ionic bonding" is given when the ionic character is greater than the covalent character - that is, a bond in which a large electro negativity difference exists between the two atoms, causing the bonding to be more polar (ionic) than in covalent bonding where electrons are shared more equally.

Bonds with partially ionic and partially covalent character are called polar covalent bonds.

Ions bonds are also commonly defined as the result of e- transfer between two atoms with the metal loosing electrons and the non metal accepting the electrons.

Examples of Ionic Bonds:

Common table salt is sodium chloride. When sodium (Na) and chlorine (Cl) are combined, the sodium atoms each lose an electron, forming cations (Na+), and the chlorine atoms each gain an electron to form anions (Cl−). These ions are then attracted to each other in a 1:1 ratio to form sodium chloride (NaCl). Na + Cl → Na+ + Cl− → NaCl

Molecular ions like NH4+ or SO4

2-

Sodium and fluorine undergoing a redox reaction to form sodium fluoride. Sodium loses its outer electron to give it a stable electron configuration, and this electron enters the fluorine atom exothermically. The oppositely charged ions -typically a great many of them- are then attracted to each other to form a solid.

Covalent Bonds/ Covalent Bonding

Are formed when two non metal interacts form a bond. Since both elements have the same tendency to accept

e- a bond is formed by sharing e- between the two atoms.

Is a chemical bond that involves the sharing of electron pairs between atoms.

The stable balance of attractive and repulsive forces between atoms when they share electrons is known as covalent bonding.

For many molecules, the sharing of electrons allows each atom to attain the equivalent of a full outer shell, corresponding to a stable electronic configuration.

Covalent bonding includes many kinds of interactions, including σ-bonding, π-bonding, metal-to-metal bonding, agostic interactions, and three-center two-electron bonds.

The term covalent bond dates from 1939. The prefix co-means jointly, associated in action, partnered to

a lesser degree, etc.; thus a "co-valent bond", in essence, means that the atoms share "valence", such as is discussed in valence bond theory. In the molecule H2, the hydrogen atoms share the two electrons via covalent bonding.

Covalence is greatest between atoms of similar electro negativities.

Thus, covalent bonding does not necessarily require that the two atoms be of the same elements, only that they be of comparable electro negativity.

Covalent bonding that entails sharing of electrons over more than two atoms is said to be delocalized.

A covalent bond forming H2 (right) where two hydrogen atoms share the two electrons.

Early concepts in covalent bonding arose from this kind of image of the molecule of methane. Covalent bonding is implied in the Lewis structure by indicating electrons shared between atoms.

Examples of Covalent Bonds:

For example, the bond formed between two Cl atoms form Cl2 is covalent, covalent bonds are also found between C and H, c and c, and cl etc.

Submitted by: Garcia, Heunice Ann F. III-Platinum

Submitted to: Ms. Ethel D. Baluyut

Teacher

The End.