GEOLOGIC BONDING
HGC_111: General Chemistry 1
CHEMICAL BONDING
Chemical bonding, the force that binds atoms into molecules or crystals, is a fundamental concept in understanding the nature of matter. It elucidates why atoms do not exist in isolation but instead combine to create the wide variety of substances encountered in our daily experiences. This bonding is crucial in determining the physical and chemical characteristics of materials, as it arises from intricate interactions involving electrons shared or transferred between atoms.
The types of chemical bonds—ionic, covalent, and metallic—contribute distinct properties to substances. Ionic bonds involve the transfer of electrons, creating charged ions that attract each other. Covalent bonds result from the sharing of electrons, fostering a strong connection between atoms. In metallic bonding, electrons move freely, contributing to the characteristic properties of metals, such as conductivity.
Understanding chemical bonding not only unveils the structural intricacies of molecules and crystals but also plays a pivotal role in fields ranging from materials science to biology. It forms the foundation for comprehending the behavior and reactivity of substances, shaping our understanding of the world at the atomic and molecular levels.
There are three main types of Chemical Bonding. Below are some characteristics of each bond .
IONIC BOND
Formed when two atoms exchange electrons to create a positive and negative ion
The ionic compound stays connected because of the attraction between ions with opposite charges
Entails the movement of valence electrons from a metal atom to a non-metal atom
COVALENT BOND
Formed when atoms share electrons to create a molecule
Can be categorized as single, double, or triple, depending on the number of shared electron pairs
Includes the sharing of valence electrons between two atoms
METALLIC BOND
Created when metal atoms lose their outermost electron to form positively charged ions
The cohesion of the metal results from the electrical interaction between the positive nuclei and the surrounding sea of negative electrons
Entails a large number of metal atoms sharing delocalized valence electrons
IONIC BONDING VS COVALENT BOND
Various chemical bonds hold molecules together, with the two fundamental types being ionic and covalent.
In ionic bonding, electrons are transferred between atoms, resulting in the formation of oppositely charged ions. The metal loses electrons, becoming a positively charged cation, while the nonmetal gains those electrons, becoming a negatively charged anion. This bond necessitates at least one electron donor and one electron acceptor.
Conversely, in covalent bonding, atoms with similar electronegativity share electrons, as neither atom strongly attracts or repels the shared electrons. This bonding occurs between identical atoms or those close in the periodic table, typically involving nonmetals. However, it can also occur between nonmetals and metals.
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POLAR VS NON POLAR
Determining whether a molecule is polar or nonpolar involves considering factors such as electronegativity difference, symmetry, molecular geometry, and the presence of a dipole moment. A significant electronegativity difference between atoms suggests polarity, while symmetrical shapes and identical atoms around a central atom indicate nonpolarity. The overall molecular geometry and the presence of polar bonds or functional groups also contribute to assessing polarity. It's crucial to analyze these factors collectively to determine the overall polarity of a molecule.
Polarity in chemical bonding refers to the distribution of electrical charge among atoms connected by the bond. It indicates whether the electron cloud is evenly spread across the atoms in the molecule or if the presence of an electronegative atom affects electron density. The way electrons are distributed influences the molecule's behavior and reactivity.
Polar covalent bonds arise when atoms with differing electronegativities share electrons, creating a covalent bond. These molecules interact with other polar substances, exhibiting positive and negative charges at opposite ends, making them electrically charged.
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THE OCTET RULE
The octet rule is a foundational concept in chemistry, asserting that atoms seek to gain, lose, or share electrons to achieve a stable electron configuration with eight electrons in their outermost shell. This rule is based on the stability observed in noble gases. Atoms can achieve an octet through ion formation (gaining or losing electrons), covalent bonding (sharing electrons), or dative bonding. While the octet rule provides a useful framework, there are exceptions, particularly for elements outside the second period of the periodic table.
Located here are the rocks/minerals that are found in the Valley Fault System on Earth Science.
This would show you how the chemical bonding contributes to the characteristics of rock/mineral or structure.
Basalt Rock - Igneous rock
[Pyroxene (Silicates)]
Basalt rocks primarily consist of various minerals, predominantly including pyroxene. Minerals like pyroxene (Silicates) in basalt consist of silicate tetrahedra.
(SiO4)4- (Silicon-Oxygen Tetrahedron)
WHAT TYPE OF CHEMICAL BONDING IT IS? IS IT POLAR OR NON POLAR?
In a silicon–oxygen bond, electrons are shared unequally between the two atoms, with oxygen taking the larger share due to its greater electronegativity. This polarization means Si–O bonds show characteristics of both covalent and ionic bonds. The difference in their electronegativity is 1.7 (Oxygen - 3.5, Silicon 1.8), which concludes that it is a polar covalent bonding.
HOW DOES THE CHEMICAL BONDING CONTRIBUTES TO THE
CHARACTERISTIC OF THE ROCK/MINERAL?
The covalent bonds between silicon and oxygen atoms within the tetrahedra result in a strong and stable structure. The bonding within silicon-oxygen tetrahedra also impacts the density and specific gravity of minerals. The strength of the covalent bonds affects the melting and solidification temperatures of minerals. Strong covalent bonding generally has higher melting points, influencing the type of rocks formed in volcanic or magmatic environments. The bonding within the tetrahedra influences the cleavage and fracture patterns of minerals.
DOES IT FOLLOW THE OCTET RULE?
Silicon atom forms a covalent bond with four oxygen atoms. Silicon and Oxygen are sharing with two electrons each oxygen. With silicon in the center and oxygen on each side, a tetrahedral structure is created. In this structure, the octet rule is met because each oxygen atom has eight valence electrons in its outer shell, sharing two electrons from the shared bond and having six own electrons. Silicon also met the octet rule by sharing two electrons with four oxygen atoms.
Chert - Sedimentary Rock
[Quartz (Silicates)]
Chert is a sedimentary rock primarily composed of microcrystalline or cryptocrystalline quartz (silica). The chemical bonding in chert mainly involves the bonding within the silica.
SiO2 (Silicon Dioxide)
WHAT TYPE OF CHEMICAL BONDING IT IS? IS IT POLAR OR NON POLAR?
(SiO2) structure, which is predominantly covalent. Because the oxygen atom is more electronegative than the silicon atom, the bonds in the molecule are polar. The difference in their electronegativity is 1.7 (Oxygen - 3.5, Silicon 1.8), which concludes that it is a polar covalent bonding. But because of its linear and symmetrical structure, SiO2 is a non-polar compound.
HOW DOES THE CHEMICAL BONDING CONTRIBUTES TO THE
CHARACTERISTIC OF THE ROCK/MINERAL?
Chert is exceptionally hard and durable because of the strong covalent bonds between the elements. Chert's covalent bonds offer chemical stability, making it resistant to dissolution by acids and less prone to alteration when exposed to environmental factors.
DOES IT FOLLOW THE OCTET RULE?
The central atom in SiO2, silicon, has four valence electrons. Each oxygen atom contributes two electrons to form a covalent bond. Allowing both oxygen and silicon to follow the octet rule by sharing electrons.
IONIC BONDING
Clay - Sedimentary Rock
[Clay minerals (Phyllosilicates )]
Clay minerals have a layered structure composed of sheets of silicon-oxygen tetrahedra and aluminum-oxygen octahedra.
Al2O3 (Aluminum-Oxygen Octahedra)
WHAT TYPE OF CHEMICAL BONDING IS IT?
The bonding between aluminum and oxygen in the octahedra involves primarily ionic bonding. Aluminum is a metal cation (Al3+) with a relatively low electronegativity compared to oxygen. Oxygen has a 3.5 electronegativity, while aluminum has 1.5. Their difference (2.0) indicates that this bonding is ionic.
HOW DOES THE CHEMICAL BONDING CONTRIBUTES TO THE
CHARACTERISTIC OF THE ROCK/MINERAL?
The layered structure of clay minerals is a result of strong covalent and ionic bonding inside the mineral structure, which is generated by the arrangement of silicon-oxygen tetrahedral and aluminum-oxygen octahedral sheets. Clay minerals exhibit flexibility because of their layered structure, which allows them to be molded or shaped without breaking. Because of the weak forces between layers, such as hydrogen bonding, these layers can glide over one another, giving clay its flexibility and malleability.
DOES IT FOLLOW THE OCTET RULE?
Aluminum gives a total of 6 electrons (3 for each atom) to oxygen, which has a total of 18 electrons (6 for each atom) to complete the octet rule (8 for each oxygen atom).
METALLIC BONDING
Sandstone - Sedimentary Rock
[Pyrite (Sulfide)]
Sandstone contain minerals including pyrite. Its occurrence within sandstone is usually sporadic and occurs as disseminated grains or small nodules rather than being a dominant mineral in the rock.
FeS₂ (Pyrite)
WHAT TYPE OF CHEMICAL BONDING IT IS?
Pyrite is made up of iron (Fe) and sulfur (S) atoms organized in a crystal lattice structure. Metallic bonding occurs between the iron atoms in this configuration. In metallic bonding, electrons are delocalized and freely travel among adjacent iron atoms, generating a "sea of electrons" that holds the iron atoms together. The distribution of electrons throughout the structure results in the metallic shine and strong electrical conductivity observed in pyrite. However, when we compute its polarity using its electronegativity, sulfur has a value of 2.5 while iron has a value of 1.8. They have a difference of 0.7, indicating that they are polar covalent bonds. But according to (Perkins, n.d.), "metallic ore minerals such as pyrite (FeS2) and stibnite (Sb2S3), generally have little ionic character; most of them, particularly those in the sulfide and sulfosalt groups, contain combinations of covalent and metallic bonding."
HOW DOES THE CHEMICAL BONDING CONTRIBUTES TO THE
CHARACTERISTIC OF THE ROCK/MINERAL?
Sandstone's primary minerals, such as quartz and feldspar, are held together by strong covalent bonds, which contribute to the rock's hardness and abrasion resistance. It also has an impact on the texture and grain size of the sandstone. When compared to finer-grained types, coarser grains often result in a more porous and permeable sandstone. The arrangement and bonding of mineral grains affects the porosity and permeability of sandstone. While metallic bonding isn't a major component in the qualities of sandstone.
DOES IT FOLLOW THE OCTET RULE?
Iron has eight valence electrons, while sulfur has six. To fulfill the octet rule, the iron atom shares two electrons with each sulfur atom, resulting in a single bond.
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