Chemical Structure

Yung-ya Lin

Chemical Structure

Chemistry and Biochemistry department

Yung-ya Lin

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from 22 users


Overall 4.9
Easiness of class 1.6
Workload 1.3
Not Clear
Clarity of professor 4.5
Not Helpful
Helpfulness of professor 4.9


  • Needs Textbook
  • Engaging Lectures
  • Appropriately Priced Materials
  • Often Funny
  • Gives Extra Credit
  • Uses Slides
  • Snazzy Dresser
  • Would Take Again


Textbook listings are currently unavailable for this course.

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Fall 2016

Grade distributions are collected using data from the UCLA Registrar’s Office.

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Quarter Taken: Fall 2016 Submitted Oct. 6, 2017 Grade Received: B+

I enrolled in honors by accident, and it the best mistake of my college caREER so far. This class really ignited my passion for chemistry, and I knew that I had made the right choice to be a chemistry major. Professor Lin is kind, enthusiastic, and really cares about his students' academic understanding. I would recommend this class to any chem or biochem major, and others in the physical sciences who are interested in quantum mechanics (and dank memes). However, you really do need to be willing to put in the work--the daily homework and weekly problem sets are not a joke. Professor Lin does sometimes get off track in his lectures, because once he starts talking about science, he just can't stop. This means that going to office hours (held daily and sometimes even on the weekends) are super important in order to really understand what you're doing (simple snacks are also provided). Professor Lin's accent can also take a few days to get used to...he can talk fairly quickly and blur some words and terms together. One of the best parts of the class for me was its small size. I was really able to connect with other people in my major and make study buddies. Also, basically all of my friends are people from 20AH...when you spend at 15 hours a week suffering alongside your peers, you build a strong bond. I would definitely take a class with Professor Lin again and hope you all get the chance to, either for your caREER or for mere ENTERTAINMENT.

Quarter Taken: Fall 2016 Submitted Oct. 6, 2017 Grade Received: A+

This class was an amazing experience and I would highly recommend it to any biochemistry or chemistry major or anyone who wants to get their mind blown by QUANTUM MECHANICS.

Professor Lin is an outstanding teacher, is super passionate about the material, and is very concerned about students. However, his passion sometimes means he gets sidetracked during lecture. But even these tangents are helpful in remembering the material. For example, I will forever associate blackbody radiation with Naples and the Alaskan wilderness.

But beware, this class does require a lot of work. We have daily homework and weekly problem sets (which can be lengthy) . Additionally, in my experience, the daily office hours (with complementary snacks) are crucial to gain a TRUE UNDERSTANDING of the material.

Exams are very straightforward as long as you do the homework, pay attention during lecture, complete the practice exams, and understand any derivations shown in class. These tests are 3 hours long but he provides Subway sandwiches. Professor Lin emphasizes conceptual understanding over memorization so all formulas are provided.

One major benefit of the class is its small size. This means you get to develop a good relationship with the professor and your classmates. I made the vast majority of my friends through this class and the massive amounts of time we spent studying together.

Overall, 1000000/10 would recommend.

Quarter Taken: Fall 2016 Submitted March 1, 2017 Grade Received: A

Lin is a very great prof. He really makes me learn a lot. After my first midterm I got a 98 and he sent me an personal E-mail and told me how great I did. He really helps you understand quantum mechanics and also holds super lots of office hours and he wants you to succeed in his class. This class requires a lot of work but you can also get a lot form this class. He is also going to write me a recommendation letter. Nice guy, very approachable some people might not be comfortable with his Chinese accent, but his speaking is okay for me. Strongly recommended.

Quarter Taken: Fall 2016 Submitted Jan. 25, 2017 Grade Received: A

Professor Lin was my first professor at UCLA and he's one I'll never forget. He really cares about his students and works hard to make sure you do well. Don't get me wrong, the class is extremely difficult and you have to put it a ton of effort, but if you try, and really pay attention to the practice tests he gives you, you'll do fine.

Quarter Taken: Fall 2016 Submitted Dec. 21, 2016 Grade Received: B+

I totally agree with my classmate's remarks one floor below me. Just add one more comment here. In addition to clear physical picture and inspiring insight, Professor Lin told good jokes, too. Why carrot should be white? How to form a group of boy scouts? Two-body to one-body to no-body transform?! (I am laughing now.) It is even more amazing to see how Professor Lin effortlessly connects his lecture to state-of-the-art research and current fundamental challenges in chemistry (how to steal zero-point energy? how to do cold fusion by quantum tunneling?). Take his course whenever possible. But it will take you enormous amount of time to study, think, and do daily previews and weekly problem sets, in order to excel in his course.

Quarter Taken: Fall 2016 Submitted Dec. 20, 2016 Grade Received: A-

Don't take this class if you can't invest 13 hours of lectures and 5 hours of self studying per week. Prof Lin's accent will confuse you in the first couple of days but you'll get use to it, so on so forth.
It is very hardcore commitment but also an eye opening experience, you'll learn mostly about quantum chemistry, stuff like Feynman Double Slit, Angular Momentum, Simple Harmonic Oscillator, and Collapse of Wavefunctions.(Shuuuuuuuuu).
Love prof. Lin, best Prof ever, 5/7, would take again.

Quarter Taken: Fall 2016 Submitted Dec. 12, 2016 Grade Received: A+

Don't be scared by how much people complained about CHEM 20AH and miss such a brilliant class!!!

>General guidelines before me babbling every aspect of this class:

DON'T take this class if:
•you're not a chemistry person and AP chem is already a struggle for you. (90% of this class is not relevant to AP chem. The only things that appear are orbitals, VSEPR and other relevant chemical structure stuff, and they're the easiest part of the whole class.)
•you're relatively slow at understanding new concepts. (Most of this class are new theories that basically overthrow whatever you've learned about chem and classical mechanics.)
•you're not ready for 15-35 hours of chem study per week besides lectures and office hours. (The real time spent on this class varies from person to person though).
•you are good at chem but bad at physics. (This class is physics-heavy.)

>Reviews about class:

((Please notice that this review is a personal one and might be prejudiced since I love Professor Lin and CHEM 20AH.))

Professor Lin is the best professor I've ever had and he gives best lectures. The lectures are clear and engaging, and professor uses some (often really funny) real life examples to introduce new concepts. This class is the only one that I've never checked my watch to see how much time remains. The Professor also stresses on the hard stuff and repeats them over and over again to make sure that everyone truly understands everything -- don't get bored and play on your phones when you think he's going over old stuff again becuase some of them might be new stuff or deeper analysis of old material. The only thing to notice that the lectures are some times way behind the previews you're doing so make sure you don't mix up the concepts.

As for the workload, it is indeed heavy but not THAT bad at all. (Honestly I felt some other course I took this quarter took much more time than chem). The Professor always gives the homework early and you get plenty of time to finish them. Do it ahead of time if possible. Don't wait for the last office hour to get hints and start working the night before the due (you can do that for daily previews but don't do that for problem sets becuase you'll probably suffer a lot).

Going to office hours is really helpful because sometimes the problems takes one or two hours to solve without hint. (But I actually found that solving problems by myself made me understand all the materials better. Personally I think taking the painful procedure of struggling to solve the problems and then going to his office hours to see how to solve them in a more intelligent way is the best way of doing the homework.). Also sometimes office hours are more like small lectures so don't miss them.

The most important thing that I earned from this class, besides all these precious knowledge of quantum chemistry, is personal attention from the professor. Everyone knows that it is SO HARD to get personal attention in such a big school, but professor Lin really cares about his students. He gives us snacks and presents, answers questions with patience, and most importantly, replies to emails really quickly. (I actually sent emails several times at 2 or 3 am and he still replied in like half an hour).

Plus, you'll make lots of friends in this class because of the small class size, and that's another good thing about CHEM 20AH!

P.S.: I'm definitely taking C113B with Professor Lin next quarter!!

Quarter Taken: Fall 2016 Submitted Nov. 3, 2016 Grade Received: NR

This course is so hard, so helpful, so enjoyable, and so exciting all at the same time. Going to Lin's 11am "quantum paradise" and 4pm office hour every weekday has become my most important daily activity. (I am thinking about going to Lin's Sunday bonus office hour when exams come.) I have decided to change my major to chemistry and take Lin's Chem 113B next quarter. It's very fortunate to have Lin as my first professor at UCLA. I have also made a few new friends in this academic family. (We studied together to try to survive.) My cousin (a graduate student at Berkeley) took Lin's Chem 115A and 115B before. He told me Lin is very supportive to his students and write very serious and powerful recommendation letters and warned me Lin has very high expectations. He is absolutely correct. We have homeworks(daily preview and weekly problme set) due every weekday. It forces me to study and do exercises a few hours every day. Perhaps that's why I did so well in the first midterm. Both Lin's 20AH and office hour snack are "additive" :)

Quarter Taken: N/A Submitted Jan. 6, 2009 Grade Received: N/A

For some reason I thought Professor was kidding every time he said the assignment was going to be hard. If it was not hard, then it took a lot of time and effort on the student's part to learn the material. Professor goes over the material many times in class so as long as you pay attention and do the homework, the class should be straightforward for the most part. Of course it is an honors course so there will be many ways to test your understanding.

I like the workload and the pacing of the class because it holds me accountable unlike other classes so I always know the material. Overall I had a great experience because Professor was entertaining in his lectures. His stories had a reason and helped when the material became too overwhelming. I doubt many professors at UCLA are as genuinely concerned and available to students as Professor are.

I would recommend taking his class if you are interested in chemistry but know that the workload requires discipline.

Quarter Taken: N/A Submitted Feb. 3, 2009 Grade Received: N/A

I took Chemistry 20AH with Professor Lin in Fall of 2008. I recently wrote a letter, which sums up to the best of my ability my impression of the class.
To Whom It May Concern:
I would like to strongly recommend Professor Yung-Ya Lin. My name is Michael Creim and I was a student in Professor Lin’s 2008 Fall Chemistry 20AH course. I will remember this class for the rest of my life. It was a truly unique experience going to 3069 Young Hall everyday for our noon lecture. Never before in my life have I seen students camped outside the classroom up to an hour early to try to get a seat in one of the front rows, a feat I accomplished most of time. Even through the end of the quarter if you weren’t there at least fifteen minutes early you had to settle for a seat in the back. In the following I will try to explain why we developed such a passion for the course and respect for the man who led it.
Chemistry 20AH was not an easy class. We had homework due everyday except Tuesday, and in the typical week I would have to spend a little more time on my Chemistry homework and studying than I had to spend on both of my other classes combined in a typical month. (Those classes were Philosophy 21 and Math 31A). In short, Professor Lin expected a lot out of us at a very high level, but he also demanded just as much from himself. He and the TA’s went above and beyond the call of duty to make themselves available to us. Every week the TAs, Ronda and Sophia, had office hours Monday and Wednesday for an hour right after class and Fridays from 4:00 to 5:00. Professor Lin, in addition to his two-hour office hours on Tuesday and Thursday nights, also had an open door policy everyday for the two hours preceding class and was available to see students for half the day on most Saturdays. Every midterm and final had an in-class review session and two out-of-class review sessions, and during finals week he held office hours for an hour everyday until the final on Friday. He worked so hard to help us succeed. He personally checked over all our work before entering the grades and returning it to us so that he could better understand what kinds of differing methodologies the class used to tackle the problems and to really get a feel for each individual’s problem solving style. Even though he gave himself this additional burden, he still always returned our grades to us on time for important deadlines. For example, I knew both my homework and first midterm grades well in time for the add/drop deadline. Professor Lin is an inspiring figure who leads by example, and genuinely cares about his students.
I think that the circumstances surrounding the second midterm really are a microcosm of the class as a whole. The midterm was scheduled for 5:00 on a Tuesday afternoon. Professor Lin said that he believed it was capable of being completed in two and a half hours but he would allow us as much time as we needed. I have a hand-eye coordination disability called dysgraphia, so I am given extended time on tests and allowed to type my answers. He volunteered to personally proctor me and allowed me to take it in a conference room next to his office. Five hours later at 10:00 the last person besides myself finished. After 8 hours at 1:00 in the morning, I finally finished as well. Professor Lin offered to give me a ride back to my apartment, which I turned down as I wanted to grab a bite to eat in Westwood. When I left he was still puttering away although I did not know on what at the time. The next day he walked into the class wearing the same clothes, then he walked out and brought in every single person’s graded midterm, all 18 pages worth of questions. I got a 90%. And to reward us for our hard work, he gave us all pizza. That day was truly special. Professor Lin is truly special.

Michael Creim

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  • Needs Textbook
  • Engaging Lectures
  • Appropriately Priced Materials
  • Often Funny
  • Gives Extra Credit
  • Uses Slides
  • Snazzy Dresser
  • Would Take Again


Textbook listings are currently unavailable for this course.

Bruinwalk is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to

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