CHM 361 | VALENCE BOND THEORY - VIDEO PRESENTATION

[00:00:08]Asalamu alaikum and good day everyone.

[00:00:10]We are group A S1205D and today we will be presenting on valance bond theory or VBT. Valance bond theory is one of fundamental theories in chemistry that explains how atoms form coalence bond.

[00:00:24]According to this theory, a coalent bond is formed when the atomic orbitals of two atoms overlap, allowing them to share a pair of electrons. The theory was first proposed by Walter Hilter and Fritz London in 1,97s and was later expanded by Lionus Polling who introduced the concept of hybridization to better explain molecule structure. Balance theory is important because it help us understand chemical bonding, molecular geometry and the strength of coalance bone.

[00:01:01]Now let's move on to the objective of our presentation. Hi, before we begin, let me briefly explain the objective of our presentation. Okay, first to understand the basic principles of valance bond theory which explain how coalent bonds are formed through the overlap of atomic orbitals. Second to explain orbital overlap band formation and hybridization including sigma bonds pi bonds and the different types of hybridization such as sp2 and sp3.

[00:01:31]Finally to discuss the applications and limitations of valance bond theory in explaining molecular structures and properties. By the end of this presentation, we hope everyone will have a better understanding of how val bond theories helps us explain chemical bonding in molecules. Hello and asalam alaikum. My name is Nural Raent and my student ID is 2024 959 and 795. As for the basic principle of valence bond theory, the valence bond theory states that a coalent bond forms when individual atomic orbital of depths localizing a pair of share electron between two specific atoms. As these atoms approach one another, the attraction between the each atom's electron and the opposite nucleus increases until they reach an optimal minimum distance. And at this point, the potition energy is minimized, creating a stable chemical bond that dictates the molecule's geometrical shape.

[00:02:34]Good day everyone. My name is Noaki Shahina Pintino Amali. My student ID is 202453925 and I will be explaining orbital overlap, sigma bond and pi bond in valance bond theory. Let's begin with orbital overlap. According to a valance bond theory, a coalent bond is formed when the atomic orbital of two atoms overlap. During this overlap, each atoms contributes one unpair electrons with opposite spins. These electrons are then shared between the two atom forming a stable coalent bond. The act of orbital overlap is very important because it determines the strength of the bone. In general, the greater the overlaps between the orbital, the stronger and more stable the coalent bond will be.

[00:03:30]There are two main types of orbital overlap. First head-on overlap which forms a sigma bond and second a side byside overlap which forms a pi bond.

[00:03:44]Now let's look at the sigma bond which is represented by the symbol sigma. A sigma bond is formed through an n to n or headon overlap of atomic orbital.

[00:03:56]This overlap can occur between 2 s orbital an orbital and a p orbital or two p orbital. As you can see from the slide, there were a diagram of each overlap because the orbital overlap directly along the line connecting the two nuclei sigma bond have the greatest orbital overlap. As a result, they are the strongest type of coalent bond.

[00:04:24]Another important characteristic is that a sigma bond is always the first bond formed between two atoms. It also allow free rotation around the bone axis because the electron density is distributed symmetrically around the bone.

[00:04:42]For example, like I show in the slide in between or CH4 all four carbon hydrogen bond are a sigma bond. Next is the pi bond represented by the symbol pi.

[00:04:56]Unlike sigma bones, a pi bond is formed through side byside overlap of two parallel p orbital like I show in the slide. Since this type of overlap is less effective than head-on overlap, pi bond are generally weaker than sigma bond. A pi bond cannot exit by itself.

[00:05:17]It is always formed after a sigma bond has already been established. Another characteristic is that pi bond restricts rotation around the bones because rotating the atoms will break the sideway overlap between b orbital. For example that I show inside slide in 18in or C2 the triple bond between the two carbon atom consists of one sigma bond and two by bond.

[00:05:50]To summarize, orbital overlap is the basic concept behind valance bond theory. Head on overlap forms strong sigma bond while side byside overlap forms weaker pi bond. Understanding these two types of bones help us explain the strange stability and bonding behavior of coalent molecules.

[00:06:15]The next one is the hybridization.

[00:06:17]Hybridization is a key part of balance bond theory. It happens when an atom mathematically makes its own outer orbitals which have similar energies but different shapes to create a brand new set of identical orbitals known as the hybrid atomic orbitals and these new path are perfectly aligned to form strong chemical bond.

[00:06:42]As for the first um hybridization which is the SP the first thing first is you have to draw the Louis structure. When you draw the Louis structure you will know how many sigma bonds are there. If there is a sigma bond you have to make sure that the electron is um partially filled just like in the food. If it's have a lone pair then you need only full or full field orbitals. However, in this case, we have a partially we only have a partially fill of those because we only have two sigma point. Thus, after filling the 2s, you will do a promotion.

[00:07:23]Why promotion? Because there is no lone pair. So it means that you do not need the full orital and instead you have to have two half fil oritals and then you do a hybridization and we will call it as S sp because one half orital SS and one half orital sp we will combine it hybridize it to become sp.

[00:07:48]As for the second one which is the hybridization for sp2. So firstly first you have to know like which how many um sigma bond is there as for the brl3 they have three sigma bond. So you have to know that you have to have three halfway orital and no full orbital because there is no lone pair. So when you do the basic filling you will fill about three of them because due to the bor valence on valance electron which is three. So when you do a promotion you have to know that the two things I say the bone the sigma bond and the long pad there is no long and three sigma bond. Thus you have to separate the full field and after the promotion you will do the hybridization and in the hybridization you will combine the s and the p house together and become sp2.

[00:08:49]Last but not least is the sp3. As for the sp3, we are focusing more on the C, which means that the C and H4 has four sigma bonds and no lone pair. So that's why in the first stage you have to um you have to fill out based on the carbon valence electron which is four. So when you fill it out and then you will do a promotion. So the promotion you have to keep mind about the sigma bond and the lone pair as we all know that there is four bond four sigma bond and no lone pair meaning that you have to have four half orital that's why in the picture there is um only four halfill orbital and no fulfilled orbital as for the hybridization you have to comine combine both houses so it will become sp3 three sp3 cuz um in S S house there is one and SP house it has three half orital. Good day everyone. I'm Maya Vihabi and my student ID is 2023 46 to 842. Now I will present the applications of balance bond theory. Okay. Firstly balance bond theory explain how coalent bonds are formed. Okay. A coalent bond is produced when two half field atomic orbitals overlap and share a pair of electrons.

[00:10:20]Greater orbital overlap results in a stronger and more stable bond. Secondly, the theory predicts molecular geometry through hybridization. For example, methane has sp3 hybridization which give it a tetra geometry while boron triilorite has sp2 hybridization resulting in a trional plan geometry.

[00:10:42]Okay. Lastly, valance bond theory helps predict molecular properties. Molecular shape and bonding influence properties such as polarity, bond angles and chemical behavior. Therefore, the theory helps us understand why different molecules have different physical and chemical properties. Although valance bond theory is useful, it has several limitations. Okay. Firstly, it cannot explain the paramagnetic behavior of oxygen molecules. Uh experimental studies show that oxygen contains two unpaired electrons where uh whereas u valance bond theory predicts that all electrons are paired. Secondly, the theory assumes that electrons are localized between two bonded atoms.

[00:11:29]Therefore, it cannot accurately describe electron deoization in molecules such as benzene. Finally, uh for molecules with more complex bonding, molecular orbital theory provides a more complex explanation of electronic structure and molecular properties.

[00:11:49]Okay. So, in conclusion, valance bond theory is a fundamental theory for understanding coalent bonding. It explain bond formation through orital overlap and uses hybridization to predict molecular geometry. In addition, it provides a basis for understanding molecular structure and properties.

[00:12:11]Although it uh although it has limitations particularly in explaining paramagnism, paramagnetism and electron deoization.

[00:12:21]Sorry. It remains an essential concept in chemistry and is complemented by molecular orbital theory. H okay. So I think I'm going to stop here. So that's all from me and my team. Thank you so much and hope you guys enjoy our explanation about balance bond theory.

[00:12:37]Bye-bye.