QUANTUM NUMBER (L-3) BY BIPLAB SIR.AT ST.JOSEPH'S GROUP OF INSTITUTION NALIPUR,JAJPUR.

Added: 2026-05-12

[00:00:01]Good morning all.

[00:00:03]Today I am going to start my third lecture of quantum number. Before we start the session now we have to recap the first lecture and second lecture of quantum number.

[00:00:18]First of all come to the live session and join. Okay students suppose this is your nucleus.

[00:00:30]Inside the nucleus proton and neutrons are present. Okay.

[00:00:43]Suppose this is your first cell. Which cell? First cell. And we know that for first cell the value of principal quantum number is one. The value of n is equal to 1. Next.

[00:00:59]Next.

[00:01:01]Suppose this is your second cell and we know that for second cell the value of n is equal to two and after second cell third cell come suppose this is your this is your third cell and for third cell the value of n is equal to three.

[00:01:36]And also students also we know that in first cell one subell is present and this subsell is your a subsell and the value of l for a subell is equal to zero. And also we know that for second cell there are two subell is present.

[00:01:55]One is s subell and another one is p subell. And the value of L for S subsell is equal to zero. And the value of L is equal to zero for P subell. And after second cell, third cell will come. And also we know that for third cell the value of N is equal to three. And since since the value of N is three for third cell that's why there are three subsells are present inside the third cell. And the subell are a subsell, P subshell and this is your B subsell. Now draw the structure students.

[00:02:37]Students this is your this is your S subell. This is your S subell and in second cell there are two subell is present. One is S another one is P. And in third cell and in third cell there are three subsell are present. One is S another one is P and third one is D.

[00:03:05]Also we know that students for S subell what I am saying for S subell the value of L is equal to zero and for P subell the value of L is equal to 1 and for A subell the value of L is equal to zero and P subell the value of L is equal to 1 l= 1 for D subell the value of L is equal to 2 students also we know that S subshell have one orbital, P subell have three orbitals and the orbitals are px, py, pz. And I am saying that if loaves are present along the x-axis, then we say this is your px orbital. Suppose loes are present along the y-axis, we say this is your py orbital. For example, suppose this is your x-axis, this is your y-axis, and this is your z axis. And we know that each axis are perpendicular to each other. Suppose loes are present along the x-axis. We say this is your px orbital. Suppose this is your y-axis. If loses are present along the y-axis, this is your py orbital. Suppose loes are present along the z axis. We say this is your pz orbital. And px, py, pz orbital are present in p subshell. And also we know that students who can say the formula the orbital present in a subsell. What is the formula? And we know that the formula is 2 L + 1. Suppose we put L is equal to 2. Because the value of L is 2 for D subsell. If we put this value the result should comes out five. That means d subsell have five orbital and the five orbitals are dxy, dyz, dz x and dx² - y square and dz square. Also we know that d orbital are classified into two parts.

[00:05:14]One is nonial d orbital. Another one is ael d orbital. nonagial orbital are dxy dyz dz x and aial orbital is dx² - y square dz². Okay students and also we know that we use sign box. We use sign box for orbitals since since one orbital is present in s of cell. Since one orbital is present in S subshell that's why we draw one box in second cell first is present S orbital and P subell have three orbital that why we draw three box this is your PX py and PZ similarly we draw one box for S, three box for P and five box for D because there are five orbital are present inside the D subsell. Okay. Now this is the recap. This is the recap of first lecture and second lecture. And we know that suppose we suppose we go towards right that means distance increases that means distance increases from the nucleus. Okay. Now start students we discuss what do you mean by degenerate orbital. What do we what do we what do we mean that?

[00:06:46]What do we mean that degenerate orbital?

[00:06:50]Dgenerate orbital.

[00:06:54]What does it mean that students? We know that the orbitals which have same energy. What I say the orbitals which have same energy and these orbitals are known as degenerate orbital. Students also know that this degenerate word this degenerate word is directly associated with energy term.

[00:07:19]Which term energy term? Because suppose there are five orbital in d subshell.

[00:07:26]For d subell for d subell there are five orbital are present dxy dyz dz x dx² minus y square and d z² and for p subshell for p subshell there are three orbital this is your px p y and pz since these have same energy since these have same energy. That's why this is known as degenerate orbital. What we say students degenerate orbital and also we know that this is called as degenerate orbital.

[00:08:11]What we say degenerate orbital. Okay students. Now come to the next point students.

[00:08:21]I want to give you complete information.

[00:08:25]What I said I want to give you complete information cell subell and orbital before we start this term I want to give you another concept this concept or this point is please focus to the focus on board and the number of what I say the number of the number of orital are present.

[00:08:58]The number of orbitals are present within the subsell. What I write students within the subsell is is given by is given by is given by the formula is 2 L + 1. What I say? 2 L + 1. And for each value of M, what I say students?

[00:09:31]For each value of M, For each value of M, there exist a there exist an orbital. First student say there exist an there exist an orbital.

[00:09:48]And the value of m lies between - l2 + l. What I say students? The value of m the value of m lies between a range between minus l2 + l. That means the value of m. What I say students the the value of m lies between the value of m lies between - l2 + l. What I say students? Please focus this point. The value of L lies between minus L2 + L.

[00:10:27]Now I want to give you the complete information of cell subell and orbital.

[00:10:36]And after completing the this concept I want to give you some formula. This formula is comes from this concept.

[00:10:45]Okay. Now starts. Suppose students this is your cell. What I say this is your cell and also we know that cell principal quantum number and we know that also athal quantum number and aumal quantum number gives idea about subsell.

[00:11:08]What I say students the aimthal quantum number gives idea about subell. After aimthal quantum number then third quantum number is your magnetic quantum number and the magnetic quantum number gives idea about your orbital.

[00:11:28]Students what who can say who can say the definition of orbital and the definition of nodes? Please write in the comment box what do you mean by orbitals. Students, we know that orbitals the region in frequ is known as orbitals. That means suppose students I write who can say tells with me. Suppose I write n = 1. What I write students? N= 1. N= 1 means your first cell or K cell.

[00:12:08]And also we know that the value of L what I say the value of L lies between 0 to first I say 0 to N -1 students remember that I say for each value of L there exist a subsell and the value of L lies between 0 to n minus one what I say 0 to n minus one if we put this n is equal to 1 the result should comes out L =0 since the value becomes the value comes out one value and this value is your L is equal to zero that's why one subell is present this is your which subsell a S subell okay and also we know that the number of orbital so what I say students the number of orbital present in a subsell the formula is 2 L + 1. If I put L =0 in this formula, the result should comes out 1. That means S subsell. What I say students? S subsell have one or students? We know that for an orbital we use box. We use box. Okay.

[00:13:29]Now students let's say suppose this is your n = 1 and this is your n = 2. If I write n = 2 students if I write n = 2 n = 2 means this is your second cell and in your second cell there are two subsell is present. One is a subell and another one is p subell. Because if we put value n the two that means 0 to 2 - 1 this is your zero l=0 and l = 1 what I say l =0 and l = 1 and we know that for a subsell the value of l is =0 for p subell the value of l is equal to 1 and also students we know that what I say we know that S subshell have one orital. S subshell have one orbital. Since S subell have one orital that's why we represent only one box. How many box?

[00:14:37]One box. Because students next for P subell there are P orbital. This is your PX, PY, PZ. What I write students? PX PY PZ PX PY and this is your PZ. Okay. The next part come to the come to the third cell and for third cell we know that the value of N is equal to 3. The value of N is equal to 3. And we know that in third cell there are three or three orbital are present or three subell are present.

[00:15:18]This is your S subsell. Suppose L=0, L = 1, L = 2. For third cell, the value of L comes out three. 1 is zero, 1 is 1 and another one is two. That means when I say L is equal to zero, that means this is your S, this is your P and this is your D. What I say students? This is your S. This is your P. And this is your D. And also students we know that we know that for S subell have one orital for P subell this is your three orbital.

[00:16:02]For D subell this is your this is your five orbital. This is your five orbital.

[00:16:09]Students we know that the value of m what I say the value of m lies between the value of m lies between - l2 + l what I say students - l2 + l that means the value is suppose this is your zero this is your zero m=0 m =0 and this is your m -1 1 0 + 1.

[00:16:42]There are three M values. This is your M = 0. This is your M = -1, 0, + 1. This is your -2 because - L2 + L the value of M lies between - L2 + L. And for D subsell, what I say students? For this subsell the value of L is equal to 2.

[00:17:08]That means the value lies between minus L to plus L. That means for this subsell the value of L lies between -2 to +2 that means -2 -1 0 + 1 and this is your + two since m have five values. What I say students?

[00:17:30]Since D since M have five values for D subsell that's why five orital are present inside the D subell now come to the next slide for for fourth cell last is for fourth cell what I say students for fourth cell there are L =0 L = 1 L = 2 and L = Since the value comes out for L=0, L= 1 and L = 2 and L = 3. That means there are four subell are present. There are four subsell are present in four cell and L =0 S L = 1 P L = 2 for D and L = 3 for F subell. Okay. Hence also students we know that also students we know that we know that S subshell have one orbital. P subshell have three orbital.

[00:18:41]D subell have five orital. F subshell have F subell have 1 2 3 4 5 6 7. Okay.

[00:18:51]Seven orbital. That means this is your M is equal to zero. M lies between -1 0 + 1 -1 0 + 1 here M is equal to -2 -1 0 + 1 and this is your + 2 that means students here for F cell -3 - 2 -1 0 + 1 + 2 and for + 3 okay students Students I want to give you the most interesting point or most interesting concept. Students please please focus on board. Please here the value of n is equal to 1. What I say students the value of n is equal to 1 and the orbital is present in first cell is equal to the subell is present in first cell. This is your a subset students. Here the value of n is equal to 2. What I say? The value of n is equal to 2. That means there are two subells are present. What I say? Two subells are present inside the second cell. Students for third cell we know that n is equal to 3. That means that means there are three subshell. What I say students? There are three orbit three subsell are present S, P and your D. Okay. Now come to the next slide.

[00:20:29]Students students focus on board. The value of n is equal to your four. Since the value of n is equal to 4 that's why there are four subsells. There are four subsell are present inside the four cell and the subsells are S, P, D and F. S, P, D and F. That means we write the most important point the number of subell. What I write the number of subsell are present are present in A. The subell are present. The number of subell are present within the cell within the within the cell is equal to students.

[00:21:29]What I write is equal to L is equal to L. Okay. And also we know that the maximum number of electron present the maximum the maximum number of electrons what I say students the maximum number of electrons present in a cell in a cell is given Apply the formula 2 n² what I students write 2 n² n² students come to the this slide students there are one orbital is present for first cell there are four orbital are present there are four orbital are present in second cell there are nine orbitals are present inside the third cell and there are there are 16 orbital are present inside the four cell. That means the number of orbitals. What I say students? The number of orbitals present in a cell.

[00:22:56]The formula is the most important point.

[00:22:58]Then the very very the most important point is the number of the number of orbital. What I write students? The number of orbitals present the number of orbitals present inside the cell inside the cell is your is your is your is your is your students. But n² what I write a² the maximum number of electron present.

[00:23:34]This is your 2n square and the number of orbitals present in n² and the number of sub cell present in your cell. This is your the value is equal to one. Okay students, this is your complete information about magnetic quantum number and after completing the magnetic quantum number now we start last quantum number and last quantum number is your students tell me with me the last quantum number is your is your spin quantum number. What I say students?

[00:24:14]Spin quantum number.

[00:24:23]Students like principal quantum number is represented by L, assumeal quantum number is represented by L and magnetic quantum number is represented by M.

[00:24:35]Similarly, the spin quantum number is represented by small s. What is right the it is it is represented by that means spin quantum number is represented by small s students spin quantum number what does it tells about or what does it suggest that spin quantum number gives idea about the spin of an electrons what I say students spin quantum number gives idea about the spin of an electron. That means we write spin quantum number gives idea about that means we write it gives it gives idea about idea about spin of an electrons. What I write spin of an electrons students what when I say the spin of an electrons what does it mean that that means electrons revolves in their own axis.

[00:25:52]What I say electron revolves their own axis. Okay. And there are two orientations. How many orientation? two orientation. One is your clockwise and another one is anticlockwise. That means there are two type of orientation or two types of orientation of an electron.

[00:26:13]That means electrons have orient clockwise direction and electrons revolves in their own axis in anticlockwise direction. Students remember that for clockwise for clockwise orientation we use the value of s is equal to plus half. What I say students? The value of s is equal to plus half and for anticlockwise orientation. What I say students? For anticlockwise we use s = minus/ what students s is equal to minus half simply it it represents students also we know that we use this symbol for an electrons. What I said students this symbol use for an electrons. If one electron is present then we use this sign and also use for this sign. Students there are two spin of an electron. One is up spin and another one is down spin. What I say students? One is up spin and another one is down spin. For off spin we use this sign. That means this is your off sign and the arrow towards above. Okay, this is your PL. This is your students your down spin. What I students? This is your down students down spin. That means we use this sign. What I say students? We use these signs for your down spin. What I students? For your down spin.

[00:28:01]Students, let's start the very very important concept. Student before I start this concept I want to say that one concept is node. One concept is node and node means where the probability finding of an electron is zero. We take completely one class for node and we starts how we write how we write electronic configuration. What I say students? How to write electronic configuration?

[00:28:42]How to write electronic configuration for an for an atom or an ions. What students I write? How to write? This is the most the most important point for your need. J class 11 and class 12th exam how to write electronic configuration for an atom or ions. Students students before we understand this concept how to write electronic configuration for an atom or ions we have to or this concept follows three rules. How many rules? Three rules. One is above principle. Another one is P's rule for maximum multiplicity. And third one is PI exclusion principle. What I say students? Page exclusion principle.

[00:29:51]Students tells with me how many rules that follows how to write this is your electronic configuration. What I say students that electronic configuration that means we have to obey three rules.

[00:30:06]How many rules? Three rules. This is your above principle. Second one is W's rule for maximum multiplicity. And third one is your third one is your page exclusion principle. That means we have to obey we have to obey three rules to write electronic configuration for an atom or an ion. First is abba principle.

[00:30:36]First is abba principle.

[00:30:42]First one is your abba principle. Second one is Hoon's rule for maximum multiplicity. Students what I said that rule for maximum multiplicity.

[00:31:03]Okay students what I say horn's rule for maximum multiplicity. Horn's rule for maximum multiplicity. This is your above principle. This is your horns rule for maximum multiplicity. And third one is your ply exclusion principle. What I say students that page exclusion principle is exclusion principle. That means students we obey we obey three rules for writing an electronic configuration for an atom or an ion. Students, next we understand what what is your above principle and what is your bones rule for maximum multiplicity and what is your power exclusion principle and how they applicable in when I write electronic configuration for an atom or an ions. Okay students let's start above principle. Let's start a principle.

[00:32:27]Students what I write a principle.

[00:32:31]Students before start this concept I am asking you one question. If you know then write our comment box. Suppose students when I write 1 is what I say 1 is what I say students 1 is suppose I write 2 s suppose I write 3s what I students suppose I write suppose I write 1 s suppose I write 2 s and suppose we write 3s that means what does it mean Students we know that this is your n = 1. This is your n = 2 and this is your n = 3. What I students? n is = 3. Students n = 3.

[00:33:27]Students that means s subell is present in your first cell. 2s means s subell present in your second cell. Ps means a sub cell present in your third cell.

[00:33:44]Students, then question is what is the difference between them or among them?

[00:33:50]But 1 S when I say 1 S, when I say 2S and one I when I say 3S that means students and also we know that students also we know that the shape of S of cell is spherical. The shape of S of cell is spherical. That means that means the shape of S of cell is your spherical.

[00:34:17]And we use positive sign because positive sign indicates nucleus present inside an atom. Positive sign indicates what? Nucleus is present inside an atom.

[00:34:29]That means suppose students that means S of cell belong to first cell. S of cell belongs to second cell. S sub cell belongs to third cell. Complete the information that that this is your nucleus. This is your first cell. That means I write n= 1. For second cell I write n = 2. And for third cell I write n = 3. When I say 1s orbital students, when I say 1s orbital, that means this is your 1 s and this is your 2s and finally and finally this is your 3s.

[00:35:04]That means that means suppose this is your 1s this is your 1s this is your 2s students know that this is your 1 s this is your 2s this is your this is your 3s students I write this is your 3s that means when I say 1 s 2 s 3 s that means the 1 s 2 s 3 cell are them in in three case ss. But when I write one, when I write two and when I write three, that means int indicates the size of a subsell. What I say students? When I say 1 2 3 1 2 3 represents the cell number. And also students we know that the first point the first point of principal quantum number. Principal quantum number gives idea about size and energy of a cell.

[00:36:09]Students what I say the size and energy of a cell. That means when when when students remember that as the value of n increases as the value of n increases energy and size also increases. So what I say students energy and size also increases that means this is your first this is your second this is your third cell when the value of m increases size of the subell also increases let's come to the pace of cell students let's come to the piece subsell let's come to the piece of cell students what I say let's come to the piece of cell students Suppose we know that in second cell piece subell is present because there is no piece subell present inside the first cell. Suppose this is your 2p. What I say students this is your 2p. That means suppose this is your 2p.

[00:37:16]This is your 3p this is your 4. What I say students? This is your 2p. This is your 3p. And this is your fourp. That means students we know that piece subell present in which cell piece of cell present in third cell and piece subell present in fourth subell.

[00:37:39]When I say here n= 2 students with me n= 2 here n = 3 here n = 4. Students, my question is how to link one concept in another concept or how we apply one concept in another concept because this is your concept of principal quantum number students. What I say this is your concept of principal quantum number. I use this concept in above principle.

[00:38:11]Okay students that means this is your 2P and this is your this is your 3P and also students our favorite color for our ro this is your 4 P that means this is your 2P this is your 3P and this is your 4 P that means when I say two when I Say three when I say four that means as the value of n increases size also increases. As the value of n increases that means size also increases. That means students see that this is your size of 2p. When I say the or when the value of n increases 2 to three size also increases. When the value increases 3 to four that mean size also increases that means n and how n can apply on aqua principle.

[00:39:19]Okay students this is your complete information about 2P students when I write 3D when I write 40 when I write 5D that means the size increases what does I say that the size increases 3D then 4 D then 5D what I say students first the list size is 3D then size increases When we move 3D to 4D then size increases when we move 4D to 5D. Students please focus on concept.

[00:40:01]You have to understand one concept properly because when your concept is strong then you are applicable to crack need and J entrance. to crack neat and j that means you have to always focus on your concept. What I say students please focus on the concept. Okay students above principle based on the term energy. What I student say that the aba principle present on or described on the basis of energy that means that means aa principle that means aqua principle completely completely based on the concept energy.

[00:41:06]Silent the concept of energy that means students we know that everybody wants to stay in stable form. Student what I say everybody wants to stay stable form.

[00:41:21]That means in chemistry always we compare who is the less stable and who is the more stable. Since everybody wants to stay instable that means students I give you a relation the relationship is between or in between energy versus stability. What I say students energy versus stability that means students this is your inverse relation. What I say students this is your inverse relation. That means when energy increases. Students, else with me, when energy increases, stability decreases. When energy decreases, stability increases. And everybody wants to stay in stable form. That means that means when energy increases. When energy increases, stability decreases. And when energy decreases, stability increases. That means suppose students suppose this is your electron. Focus in this is your electron. Suppose I want to give you one place is your A place. I want to give you another place. This is your B place. Okay. Plus suppose A have lower energy. What I say students? A have lower energy. H in compared to B in compared to A, B have I high energy.

[00:43:04]B have high energy. Suppose one electron comes.

[00:43:10]My question is my question is this electron prefers which place either A or either B. Students my question is topos electrons and they have two place to stay here.

[00:43:28]One is A, another one is B. And we know that A have lower energy as compared to B and B have higher energy as compared to A. That means students the most important point everybody or everyone in our chemistry wants to stay in stable form or wants to attain or wants to get stability. That means here we know that energy is inversely proportional to stability. That means who have higher energy they have lower stability.

[00:44:09]Who have higher energy they have who have lower energy they have higher stability. That means when electron comes they choose lower energy place.

[00:44:24]They choose what or he choose lower energy place because lower energy. When the energy is lower stability is more.

[00:44:35]When energy is higher, stability is lower and everybody wants to stay in stable form. Wants to stay in stable form. That means electron prefers lower energy state rather than higher energy state. Because when electron present in lower energy they feel or he feel more stable as compared to when electron present in present [snorts] in your higher energy state or higher energy place and this place is your B place. This place is your B place. That means suppose I write suppose I write 1 S. Suppose I write 2 S. Suppose I write 2 P. Suppose I write 3S then 3 P then 3D. What I say students? 1 S, 2 S, 2 P, 3 S, 3 P and 3D. Suppose students you know that finally electron stay in your cell or we say that in your subsell or we say that in your orbitals. Finally electrons stay in cell or in subsell or in orbital. That means we have to calculate or we have to know that before entering the electron subell because suppose we have 1 s suppose we have 2s 2 p 3s 3p and 3d suppose one electron is com okay what I say one electron is come they have they have this type of possible place he can stay what I say Students, there are different kind of place the electron can stay. That means electron choose who have lower energy then he select the lower energy place and finally he stays here because those who have lower energy he have more stability. That means we have to calculate 1 s, 2 s, 2p, 3s, 3p and 3d who have lower energy. What I say students who have lower energy and above gives idea about how to calculate.

[00:47:06]Students tell me with me how to calculate who have lower energy and who have higher energy. Students again I repeat that above gives idea about energy concept that means when electron comes they have five place and he have five place then he has to choose one place and which place is more preferable for an electron that means we have to use energy concept and then who have lower energy electron finally goes to lower energy the cell. That means students we use n + l value of this is your the most interesting concept. The concept is n + l value that means n + value is directly proportional to energy. What I say students n + l value is directly proportional to energy. That means when we want to calculate what we want we want to calculate energy who have lower energy and we who have higher energy then we have to use this formula. What I say students?