Hey khan, just a quick message, not sure if you'll see this but I use to watch your videos through school and university, now I am working professional thanks to the classes I passed with your help. Hugely grateful for you help. Your student From Australia
I spent 18 hours straight last quarter listening to (mostly) your lectures. Well, cramming went awesome, and I did alright on the midterm, but due to a lack of lab attendance, I'm back again for your awesome videos. Just wanted to say thank you for being a life saver!
I've never really understood why the d shells were in one energy state behind, but what khan said makes sooo much sense. Hands down best teacher on youtube.
THANK YOU!! you're videos really help. i'm in AP chem now... I watch these videos right before a test or when I don't understand a concept taught in class. my teacher in regular chemistry taught us that it's a sin (Sn) to forget tin... :)
All of this was daunting in the first few minutes of the module, but I quickly caught on. I really like how pedagogic these videos are. I feel Khan's thinking style is very close to mine. Being explicit is good.
thanks mate!!!!! I've been stressing about how on earth to count valence electrons without drawing out the whole frikin chart which would be a waste of time in an exam, but you've shown me an easier way to count them! Thankyou again!
This is amazing, all through this year after having non-science a levels - this has been my saviour for my foundation course and subsequent degree. Thank you for making these videos!
That explanation of backfilling around 5:10. Absolutely amazing. What a beautiful image; it's easier to fill 4s than 3d, makes sense, and it's cool to see the density of electrons can get so high, like intricate ethereal puzzle pieces fitting together. It's got me wondering about how close orbitals can get, what with pauli and ∆p∆x ≥ h/4π. What period do the f orbitals start, and how far back do they backfill?
THANK YOU, you literally just taught me everything my teacher failed to teach me in one week, in 15 minutes... and i have an exam tomorrow. khan forever
Man, I totally get that the model is just that - a model - but good grief that took a concept that was so abstract and frustrating to me and really helped me understand it. I really appreciate your multi-modal approaches with these videos, thank you!
I really like that he uses reason to describe the orbital clouds. This is the best explanation I have heard short of unification theory. Way better than public schooling :)
Okay so I just noticed something that helped me in writing out the electron configurations for elements. 1.When filling out the S shells you will be filling for the first two groups with the exception of He 2.The P shell fills electrons for groups 3-8 3.The D shell fills the electrons that are transition metals I hope this helps and if there is anything else that can be added to this or some of my information is incorrect then comment below on what should be fixed.
I like Khan Academy but honestly I barely learned anything from this video mainly cuz you keep moving from topic to another topic but nonetheless thanks for educating me!!
Hello:) I'm from Italy..your lessons are really awesome, and your way of teaching isn't as the way of teaching of my chemistry teacher, , thank you so much, i will follow you for all my university career , and please continue to do other lessons of chem, anatomy and biology.. bye bye from Italyyyyyyy :) anyway sorry for my poor English ..and hope to see other lessons on youtube ... !!!!!
Thank you so much for this, after listening to your lesson on the periodic table I am now understanding this better than having two science teachers explain this configuration.
In the Kaplan mcat book, every outter electron regardless of energy level is a valence electron. So for example Ir would have 2 s valence electrons and 7 d valence electrons for a total of 9
Dear Prof. Khan, is it possible to write Fe as [Ca]3d6? or would it be better to write it as [Ar]4s23d6 since it shows that 4 is the highest energy shell?
at 9:50, for Sn, if we ionized it, removing 5p2 and 5s2, and then had enough energy to rip yet another electron off, which electron would go first? In other words, given [Kr]4d10 configuration of Sn, which would be the next electron to be lost? From d orbital?
Hi, as to why d fills n-1 rather than n (5:18) may it be a screen effect : Electron already in place screen the nucleus and allow new electron to be closer with the same energy ?
What you're saying makes sense, but my textbook says that electrons are categorized into 3 groups. The inner electrons, the outer electrons, and the valence electrons. for main group elements the outer electrons are the valence electrions. but for the transition elements, all the (n-1) d elections are the valence electrons, and the outer electrons are those in the highest energy level (the highest n value)
@clemens2003 The rule is a function of the nuclear size, and the distance of the outer shell to the nucleus. It's simply that 8 electrons in the outer shell is more stable. That's when all forces are in balance. (atomic, magnetic, strong, weak, gravity) For star systems, the distances are so great that only one force is involved, gravity. The orbiting bodies will configure for lowest energy state for gravity. Also the bodies are not uniform, like electrons, protons, and neutrons.
wow , you my friend can be a very successful university teacher , you explain this things like an alien , u seem to be very smart :) , thanks a lot for sharing ur wisdom mate
I think you've misunderstood what [Kr] means in this notation. It's basically a placeholder for the full electron configuration of krypton. So [Kr] stands for: 1s² 2s² 2p⁶ 3s¹ 3p⁶ 4s² 3d¹⁰ 4p⁶ That's a lot to write down, so it's shortened to [Kr]. When Sal writes [Kr] 5s² 4d¹⁰ 5p² for tin, that means we have 14 more electrons than are found in Krypton and they're in the 5s, 4d and 5p orbitals.
So if the electron configuration of Cr is [Ar] 4s^1 3d^5 due to Hund's rule. Then Cr has 1 valence electron right? I'm sure someone already asked this question but it doesn't seem very recent... Thank You
@Giallorossi03 you guys...the periodic table consist of elements that are named in Latin and Greek. Tin is the English notation for this element. But yeah, it is kinda funny =D
we don't say valence electrons in Britain. Instead, when an atom goes beyond 1 shell, we say 2nd shell, 3rd, 4th, 5th and so on. still a useful video, good job
perhaps you should look up the recent articles by Eugen Schwarz in the Journal of Chemical education. I assure you what I am saying is correct. Most textbooks have it wrong. 3d actually fills before 4s. That's precisely why 4s is preferentially ionized. I have been teaching general chemistry for 30 years, the past 15 to classes of 350-450 students in US colleges, most recently UCLA. I am not a kid off the street just trying to disrupt this website or trying to undermine the amazing Kahn.
You're really great ! thanks you ! btw - you forgot to mention that helium doesn't infact have 8 electrons (it's written under 8) also wrote that Cu Ag and Au would have 2 electrons in their outer shell although they actually have 1 since they give away 1 to fill their d shell. But thanks alot !
I need to kno or i cant concentrate while im watching are u using a mouse to write or like a computerized pen sorta thing, I NEED TO KNOW PLEASE thats all im thinkin when im watching the videos i need the closure....thanks
they use 8 because it takes more energy to open up a new shell, when their are 8 the electrons won't jump to other atoms to either get rid of or aid the extra electrons so its more stable and balanced
when i write an electron configuration in noble gases, how do i know how many valence electrons there are? for example [Ar] 4s2 3d10 4p5 has 7 valence electrons. how does that work?! wouldn't it be 17?
Valence eletrons are not only those on the outer shell. "The valence electrons are instead defined as those outside a noble-gas core" (Wikipedia: wikipedia(dot)org/wiki/Valence_electron)
@PINKmeUP67 It's 7 because the highest energy level is 4. [Ar]4s2 3d10 4p5 The 4s2 and the 4p5 add to 7. That 3d10 portion is what he was talking about when he mentioned the back filling. Make sense?
Wait, so Helium has 2 protons and 8 electrons in it's outer shell? Is that correct or am I missing something? I thought an element in equilibrium had the same number of electrons as protons.
Vector Boris Oh ok, that threw me off, is it usually located in the S block on normal charts? I notice it's colored like the ones in the P block, that crap makes it super confusing!
Sal you said in this video that atoms are best paired up when there are 8 electrons on the outside? Does this in anyway to your knowledge, theory, fundamental ideas have any relation to our solar system only having 8 planets? Has this been researched or have any theories been formed? Just something that crossed my mind today.
More importantly, the 4s orbitals DO NOT fill before the 3d in transition metal atoms. THis is a common textbook error. The 3d are filled first but the final 2 electrons enter the 4s orbital to minimize repulsion. Please see the blogs on my website on this topic
Hey khan, just a quick message, not sure if you'll see this but I use to watch your videos through school and university, now I am working professional thanks to the classes I passed with your help. Hugely grateful for you help.
Your student
From Australia
I spent 18 hours straight last quarter listening to (mostly) your lectures. Well, cramming went awesome, and I did alright on the midterm, but due to a lack of lab attendance, I'm back again for your awesome videos. Just wanted to say thank you for being a life saver!
I've never really understood why the d shells were in one energy state behind, but what khan said makes sooo much sense. Hands down best teacher on youtube.
I didn’t try to think
Ohhh, this is why... I didn't even think about it
THANK YOU!! you're videos really help. i'm in AP chem now... I watch these videos right before a test or when I don't understand a concept taught in class.
my teacher in regular chemistry taught us that it's a sin (Sn) to forget tin... :)
Thank you SO MUCH for making this video. I had college chemistry and have forgotten it. This was a great review!
All of this was daunting in the first few minutes of the module, but I quickly caught on. I really like how pedagogic these videos are. I feel Khan's thinking style is very close to mine. Being explicit is good.
thanks mate!!!!! I've been stressing about how on earth to count valence electrons without drawing out the whole frikin chart which would be a waste of time in an exam, but you've shown me an easier way to count them! Thankyou again!
This is amazing, all through this year after having non-science a levels - this has been my saviour for my foundation course and subsequent degree. Thank you for making these videos!
Thanks Sal! You're doing an amazing thing!
That explanation of backfilling around 5:10. Absolutely amazing. What a beautiful image; it's easier to fill 4s than 3d, makes sense, and it's cool to see the density of electrons can get so high, like intricate ethereal puzzle pieces fitting together. It's got me wondering about how close orbitals can get, what with pauli and ∆p∆x ≥ h/4π. What period do the f orbitals start, and how far back do they backfill?
You are better than the lecturer in my uni :) keep it up
Shenan De Silva so true
Great video. I liked it very much. More capturing then other professors I had to listen. The language is easy an not so boring. Thank u.
THANK YOU, you literally just taught me everything my teacher failed to teach me in one week, in 15 minutes... and i have an exam tomorrow. khan forever
Man, I totally get that the model is just that - a model - but good grief that took a concept that was so abstract and frustrating to me and really helped me understand it. I really appreciate your multi-modal approaches with these videos, thank you!
ahhh omg, the feeling i get, when you kinda rhetorically ask a question and i can actually answer it and follow along..ahhhh ily dude. life saver.
And now you are old
I really like that he uses reason to describe the orbital clouds. This is the best explanation I have heard short of unification theory. Way better than public schooling :)
Okay so I just noticed something that helped me in writing out the electron configurations for elements.
1.When filling out the S shells you will be filling for the first two groups with the exception of He
2.The P shell fills electrons for groups 3-8
3.The D shell fills the electrons that are transition metals
I hope this helps and if there is anything else that can be added to this or some of my information is incorrect then comment below on what should be fixed.
you are the best khan. i am so glad to know you
wow ur videos helppp soo much i was studying for my chem exam and i had forgotten everything and ur videos helpedd me alot!!!! Thanks a ton
Finally, I am getting this. Thank you Dr. Khan!
So many years that none of this really made sense, it's finally dropping in thanks to Sal.
Can you recommend a companion textbook for these videos, preferably free online? It would help with understanding some of the material.
I like Khan Academy but honestly I barely learned anything from this video mainly cuz you keep moving from topic to another topic but nonetheless thanks for educating me!!
This guy is a boss! Helped me out sooo muchhh!!
Hello:) I'm from Italy..your lessons are really awesome, and your way of teaching isn't as the way of teaching of my chemistry teacher, , thank you so much, i will follow you for all my university career , and please continue to do other lessons of chem, anatomy and biology.. bye bye from Italyyyyyyy :) anyway sorry for my poor English ..and hope to see other lessons on youtube ... !!!!!
it worked perfectly in my undergrad classes, and follows my book's descriptions as well.
Thank you so much for this, after listening to your lesson on the periodic table I am now understanding this better than having two science teachers explain this configuration.
Great analysis of the Periodic Chart! 😊
both the lady and Mr.you are good teachers!😊
In the Kaplan mcat book, every outter electron regardless of energy level is a valence electron. So for example Ir would have 2 s valence electrons and 7 d valence electrons for a total of 9
Silinium! I laughed a bit at that one xD Great videos though, as always!
Awsome! Thank you for this beautiful explanation!
Loving these videos so much! It's all very exciting stuff and appreciate it a lot
Dear Prof. Khan, is it possible to write Fe as [Ca]3d6? or would it be better to write it as [Ar]4s23d6 since it shows that 4 is the highest energy shell?
at 9:50, for Sn, if we ionized it, removing 5p2 and 5s2, and then had enough energy to rip yet another electron off, which electron would go first? In other words, given [Kr]4d10 configuration of Sn, which would be the next electron to be lost? From d orbital?
Hi, as to why d fills n-1 rather than n (5:18) may it be a screen effect : Electron already in place screen the nucleus and allow new electron to be closer with the same energy ?
What you're saying makes sense, but my textbook says that electrons are categorized into 3 groups. The inner electrons, the outer electrons, and the valence electrons. for main group elements the outer electrons are the valence electrions. but for the transition elements, all the (n-1) d elections are the valence electrons, and the outer electrons are those in the highest energy level (the highest n value)
Thank you so much for this video it answer all my questions. I don't know why my professor wasn't able to explain it this way.
@clemens2003 The rule is a function of the nuclear size, and the distance of the outer shell to the nucleus. It's simply that 8 electrons in the outer shell is more stable. That's when all forces are in balance. (atomic, magnetic, strong, weak, gravity) For star systems, the distances are so great that only one force is involved, gravity. The orbiting bodies will configure for lowest energy state for gravity. Also the bodies are not uniform, like electrons, protons, and neutrons.
do you subtract the atomic number from the atomic mass to find the electrons?? how do you find the neutrons?
Thank you Dr. Khan
@monkeypenguinftw oh, ok, then how do you find the electrons??
wow , you my friend can be a very successful university teacher , you explain this things like an alien , u seem to be very smart :) , thanks a lot for sharing ur wisdom mate
This was ridiculously helpful, thank you
Hi. What would be electron configuration for Copper in ground state? and the number of outermost electrons?
Great visualization of back filling
Do you have anything on quantum numbers and energy required to to move to another energy shell? I am studying Chemistry.
I think you've misunderstood what [Kr] means in this notation. It's basically a placeholder for the full electron configuration of krypton. So [Kr] stands for:
1s² 2s² 2p⁶ 3s¹ 3p⁶ 4s² 3d¹⁰ 4p⁶
That's a lot to write down, so it's shortened to [Kr]. When Sal writes [Kr] 5s² 4d¹⁰ 5p² for tin, that means we have 14 more electrons than are found in Krypton and they're in the 5s, 4d and 5p orbitals.
This video helped me so much thank you!
you make everything make so much sense... throughout these visa i keep having "EUREKA!! moments"
what happens when i need to solve in the D groupe for example the one with 72 protons ans 72 electrons or 104 electrons how do you count that one??
Sal, you deserve at least half of my tuition.
@khanacademy
I think you made a mistake at 7:18!
The are exceptions: Chromium and copper:
[Ar] 4s1 3d5 , [Ar] 4s1 3d10
Sir Soap this is why i am always confused by chemistry concept. So many exception in chemistry and lecturer dont even know why. Lol
Thanks it really did help me a lot
Listening to Salman Khan's lectures is like having Ray Romano as a crazy substitute teacher. Best day EVER.
what video should i watch before this one? I don't understand some of the material.
So if the electron configuration of Cr is [Ar] 4s^1 3d^5 due to Hund's rule. Then Cr has 1 valence electron right? I'm sure someone already asked this question but it doesn't seem very recent... Thank You
BAdBrAd yes that is so
02:00 can it also be written as [ca]3d^6, since calcium is the nearest outside of the D-block?
@Giallorossi03 you guys...the periodic table consist of elements that are named in Latin and Greek. Tin is the English notation for this element. But yeah, it is kinda funny =D
we don't say valence electrons in Britain. Instead, when an atom goes beyond 1 shell, we say 2nd shell, 3rd, 4th, 5th and so on.
still a useful video, good job
@ligitcounterfit no he meant to say as the atom gets larger
perhaps you should look up the recent articles by Eugen Schwarz in the Journal of Chemical education. I assure you what I am saying is correct. Most textbooks have it wrong. 3d actually fills before 4s. That's precisely why 4s is preferentially ionized. I have been teaching general chemistry for 30 years, the past 15 to classes of 350-450 students in US colleges, most recently UCLA. I am not a kid off the street just trying to disrupt this website or trying to undermine the amazing Kahn.
You're really great ! thanks you !
btw - you forgot to mention that helium doesn't infact have 8 electrons (it's written under 8)
also wrote that Cu Ag and Au would have 2 electrons in their outer shell although they actually have 1 since they give away 1 to fill their d shell.
But thanks alot !
I need to kno or i cant concentrate while im watching are u using a mouse to write or like a computerized pen sorta thing, I NEED TO KNOW PLEASE thats all im thinkin when im watching the videos i need the closure....thanks
wow! this is really helpful!! thank you so much!!!
Makes perfect sense, thanks!
That was amazing explanation
Good question. What did/are u studying Sal? I know this stuff from school but still.
Are we going to pretend like Sn isn't Tin?
hahahaha you had me gasping..
Minenhle Zukula Zama i am shook! I noticed too.
Look it up pls
Minenhle Zukula Zama
No way...
Minenhle Zukula It is tin but its Latin name is stannum dats y the chemical symbol is sn
they use 8 because it takes more energy to open up a new shell, when their are 8 the electrons won't jump to other atoms to either get rid of or aid the extra electrons so its more stable and balanced
Thanks for the laugh! You made my day.
when i write an electron configuration in noble gases, how do i know how many valence electrons there are? for example [Ar] 4s2 3d10 4p5 has 7 valence electrons. how does that work?! wouldn't it be 17?
had not ever gone this far - teachers literally orchestrated me away from science classes
Valence eletrons are not only those on the outer shell.
"The valence electrons are instead defined as those outside a noble-gas core"
(Wikipedia: wikipedia(dot)org/wiki/Valence_electron)
Thank you very much. I can't express how much I need to than you.
@PINKmeUP67 It's 7 because the highest energy level is 4. [Ar]4s2 3d10 4p5
The 4s2 and the 4p5 add to 7.
That 3d10 portion is what he was talking about when he mentioned the back filling. Make sense?
Nice demonstration! BTW, Sn is Tin.
Wait, so Helium has 2 protons and 8 electrons in it's outer shell? Is that correct or am I missing something? I thought an element in equilibrium had the same number of electrons as protons.
Vector Boris
Oh ok, that threw me off, is it usually located in the S block on normal charts? I notice it's colored like the ones in the P block, that crap makes it super confusing!
Sal you said in this video that atoms are best paired up when there are 8 electrons on the outside? Does this in anyway to your knowledge, theory, fundamental ideas have any relation to our solar system only having 8 planets? Has this been researched or have any theories been formed?
Just something that crossed my mind today.
A spider has 8 legs, coincidence or conspiracy?
Thank you! I get it much more now:)
This guy gets me through AP Chemistry :P
CU will have one electron in its outer most shell because it has the electronic configuration of [Ar],3D''10,4S"1
which is the first video? I'm not getting it
My table shows Iron (Fe) as, [Ar]3d^64s^2... why did you write it the opposite? does it matter?
Can you please do the topic Hybridization?
Why are there only 2 orbital for p shell on the picture with the explanation of p orbitals?
I am so going to Ace my final thank you so much!
Sir, u said that when we come to d block, we had to take it number as (period number - 1), then for Kr y don't u took!!!?
More importantly, the 4s orbitals DO NOT fill before the 3d in transition metal atoms.
THis is a common textbook error. The 3d are filled first but the final 2 electrons enter the 4s orbital to minimize repulsion. Please see the blogs on my website on this topic
What if you put hydrogen next to chlorine? Would it stop existing?
what happened to u in the last vid of this playlist
please make some examples for the f-group, i don't get why Uranium has [Rn] 5f3 6d1 7s2 and Plutonium [Rn] 5f6 7s2. What happens with that 6d1 ? o.o
this is why youtube and the information age we are currently in are so cool.
education is now nearly free
man thanks alot for these vids man. Awesome! :)
Awesome!
I studied Robotics Engineering for 5 years and never heard this explained better.
you are my master!
thanks to Sal I now love the periodic table...
@Breyerlov mass- atomic number .. you always subtract a smaller number from the bigger one ;)
haha I always tell everyone about Sal, dudes my freakin hero