Ionic, Covalent, and Metallic Bonds

TABLE OF CONTENTS

Ionic, covalent, and metallic bonds are different types of chemical bonds. An ionic bond is formed when one atom donates valence electrons to another atom. A covalent bond is formed when both atoms share pairs of valence electrons. A metallic bond is formed between a cloud of free electrons and the positively charged ions in a metal.

In ionic and covalent bonds, the valence electrons play a critical role in forming the bond. Atoms achieve a stable electronic configuration by transferring and sharing electrons. As a result, the bonds become stable with well-defined strength and energy.


Geological

history

 of the Andes


Tectonic pressures and volcanic activity gave shape the earth, South America been lifted up from sea levels, started showing the mountains we climb this days.

The Nazca plate in the base of the Pacific Ocean and the Brazilian Shield crashed together and created mountain structures. A large portion of magma was also pushed upwards by the same phenomenon. All of this aroused volcanic activity along the coast. Several volcanic cones emerged and formed most of the volcanic range. Some of the volcanoes are still active and smoke from time to time.

The rocky outcrops formed the Eastern sections of the range (including Apolobamba, Cordillera Real, and Quimsa Cruz ranges in Bolivia), and the volcanic cones made up


How the Andes mountain was made

The tectonic activity in the Andean region has led to intense volcanic activity, significant uplift, and the creation of towering peaks. The Andes showcase the dynamic geological processes occurring at convergent plate boundaries, contributing to the formation of one of the longest mountain ranges in the world.


The breakup of Pangaea dispersed these plates outward, and the collision of two of these plates—the continental South American Plate and the oceanic Nazca Plate—gave rise to the mountain-building activity that produced the Andes Mountains

When did the Andes mountains form?

The Andes Mountains were formed as a result of subduction between the Nazca Plate and the South American Plate. 

The Andes were formed by tectonic activity whereby earth is uplifted as one plate (oceanic crust) subducts under another plate (continental crust).  To get such a high mountain chain in a subduction zone setting is unusual  which adds to the importance of trying to figure out when and how it happened.  However, the timing of when the Andean mountain chain uplift occurred has been a topic of some controversy over the past ten years. 

The prevailing view is that the Andes became a mountain range between ten to six million years ago when a huge volume of rock dropped off the base of the Earth’s crust in response to over-thickening of the crust in this region.  When this large portion of dense material was removed, the remaining portion of the crust underwent rapid uplift. 

The Types of Rocks in Andes Mountain and its Chemical Bonding

Andesite

Type of Chemical Bonding: Andesite contains minerals covalent bonding. The melting point of andesite is relatively high due to the presence of covalent bonds. Covalent bonds require a significant amount of energy to break, resulting in a higher melting point compared to materials with weaker bonds. This property makes andesite resistant to melting under normal geological conditions.



Basalt

Type of Chemical Bonding: The chemical bonding in basalt is a combination of both ionic and covalent bonding. The presence of ionic bonding in basalt is primarily due to the plagioclase feldspar minerals. Plagioclase feldspar is composed of elements such as aluminum, silicon, and oxygen. In this mineral, the aluminum and silicon atoms form covalent bonds with oxygen, while the aluminum and silicon atoms also have a tendency to lose electrons and form positive ions. The oxygen atoms, on the other hand, have a tendency to gain electrons and form negative ions. This results in an ionic bonding between the positively charged aluminum and silicon ions and the negatively charged oxygen ions.

The covalent bonding in basalt is mainly observed in minerals such as pyroxene and olivine. These minerals are composed of elements such as silicon, oxygen, and various metal ions. The silicon and oxygen atoms form covalent bonds, while the metal ions can form both ionic and covalent bonds depending on the specific elements involved. 

Schist

The chemical bonding in schist is primarily covalent. In schist, the covalent bonding occurs between atoms within the minerals that make up the rock. The main minerals in schist include mica, quartz, and feldspar. These minerals are composed of elements such as silicon, oxygen, aluminum, potassium, and others. Covalent bonding involves the sharing of electrons between atoms to form stable bonds. 

The covalent bonding between mineral grains in schist allows for the alignment of the minerals in parallel layers or bands. This alignment gives the schist its foliated texture, where the minerals are elongated and parallel to each other. The covalent bonding enables the minerals to maintain their structure and alignment during the metamorphic process. 

Limestone

limestone does involve ionic bonding. Limestone is primarily composed of the mineral calcite, which is a form of calcium carbonate (CaCO3). Calcium carbonate is formed through the combination of calcium ions (Ca2+) and carbonate ions (CO32-). The bonding between the calcium and carbonate ions in limestone is ionic in nature. Calcium has a tendency to lose two electrons, resulting in a positively charged calcium ion (Ca2+). Carbonate, on the other hand, has a tendency to gain two electrons, resulting in a negatively charged carbonate ion (CO32-). The electrostatic attraction between the positive calcium ions and the negative carbonate ions forms the ionic bonds in limestone.

The presence of ionic bonding in limestone contributes to its characteristic properties, such as its hardness, solubility in acidic solutions, and the ability to effervesce (fizz) when exposed to acids. These properties are a result of the nature of the ionic bonding and the interaction between the calcium and carbonate ions in the limestone structure. 

Pyrite

Pyrite, also known as "fool's gold," is a mineral that exhibits metallic bonding. While pyrite is not technically a rock, it is commonly found within various rock formations, including those in the Andes Mountains. The metallic bonding in pyrite occurs between the iron (Fe) atoms within the mineral. In pyrite, each iron atom is surrounded by sulfur (S) atoms, forming a crystal lattice structure. The iron atoms in pyrite lose electrons to become positively charged ions (Fe2+), while the sulfur atoms gain those electrons to become negatively charged ions (S2-). The resulting electrostatic attraction between the positive and negative ions forms the metallic bonds in pyrite. 

Pyrite has a metallic luster, giving it a shiny appearance similar to gold. This is a result of the presence of metallic bonding, which allows for the reflection and absorption of light. 

what is the difference between polar and non- polar? 

when things are different at each end, we call them polar. some molecules have positive and negative ends too, and when they do, we call them polar. if they don't, we call them non-polar. things that are polar can attract and repel each other (opposite charges attract, like charges repel).

NON-POLAR COVALENT BONDS- If a diatomic molecule that consist of two identical atoms, such as
hydrogen or chlorine, the bonding of electrons are symmetrically centered between two atoms
 that are attracted equally to the nuclei of both atoms. That is because the two atoms in the
covalent bonds are identical and have the same electronegativity values.


POLAR COVALENT BONDS- When two atoms that are not identical form a covalent bond, the
bonding electrons will be attracted more strongly by the electronegative element, and this results in an asymmetrical distribution of the bonding electrons. 

Nonpolar Molecules
-Electronegativity difference is < .20
• Molecule is Equal on all sides
– Symmetrical shape of molecule (atoms surrounding central atom are The Same on all sides).
In symmetrical molecules with polar bonds, the dipoles cancel one another, and the resultant dipole equals zero.

Polar Molecules
The center of the positive and negative charges do not coincide.
-Electronegativity difference is between .21 and 1.99
•Molecule is Not Equal on all sides
– Not a symmetrical shape of molecule (atoms surrounding central atom are not the same on all sides) In asymmetrical molecules with polar bonds, the dipoles do not cancel one another.

Octet Rule

The Octet Rule requires all atoms in a molecule to have 8 valence electrons--either by sharing, losing or gaining electrons--to become stable. For Covalent bonds, atoms tend to share their electrons with each other to satisfy the Octet Rule. It requires 8 electrons because that is the amount of electrons needed to fill a s- and p- orbital (electron configuration); also known as a noble gas configuration. Each atom wants to become as stable as the noble gases that have their outer valence shell filled because noble gases have a charge of 0. Although it is important to remember the "magic number", 8, note that there are many Octet rule exceptions.

Example: As you can see from the picture below, Phosphorus has only 5 electrons in its outer shell (bolded in red). Argon has a total of 8 electrons (bolded in red), which satisfies the Octet Rule. Phosphorus needs to gain 3 electrons to fulfill the Octet Rule. It wants to be like Argon who has a full outer valence shell.

Example 1: HCl

Below is a Lewis dot structure of Hydrogen Chloride demonstrating a single bond. As we can see from the picture below, Hydrogen Chloride has 1 Hydrogen atom and 1 Chlorine atom. Hydrogen has only 1 valence electron whereas Chlorine has 7 valence electrons. To satisfy the Octet Rule, each atom gives out 1 electron to share with each other; thus making a single bond.

Double Bonds
A Double bond is when two atoms share two pairs of electrons
with each other. It is depicted by two horizontal lines between two atoms in a molecule. This type of bond is much stronger than a single bond, but less stable; this is due to its greater amount of reactivity compared to a single bond.

Example 2:
Below is a Lewis dot structure of Carbon dioxide demonstrating a double bond. As you can see from the picture below, Carbon dioxide has a total of 1 Carbon atom and 2 Oxygen atoms. Each Oxygen atom has 6 valence electrons whereas the Carbon atom only has 4 valence electrons. To satisfy the Octet Rule, Carbon needs 4 more valence electrons. Since each Oxygen atom has 3 lone pairs of electrons, they can each share 1 pair of electrons with Carbon; as a result, filling Carbon's outer valence shell (Satisfying the Octet Rule).

Triple Bond

A Triple bond is when three pairs of electrons are shared between two atoms in a molecule. It is the least stable out of the three general types of covalent bonds. It is very vulnerable to electron thieves!

Example 3: Acetylene

Below is a Lewis dot structure of Acetylene demonstrating a triple bond. As you can see from the picture below, Acetylene has a total of 2 Carbon atoms and 2 Hydrogen atoms. Each Hydrogen atom has 1 valence electron whereas each Carbon atom has 4 valence electrons. Each Carbon needs 4 more electrons and each Hydrogen needs 1 more electron. Hydrogen shares its only electron with Carbon to get a full valence shell. Now Carbon has 5 electrons. Because each Carbon atom has 5 electrons--1 single bond and 3 unpaired electrons--the two Carbons can share their unpaired electrons, forming a triple bond. Now all the atoms are happy with their full outer valence shell.