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.

1 of 2


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

Quarter Taken: N/A Submitted Dec. 3, 2005 Grade Received: N/A

OMG, Professor Lin is one of the best professors so far!! He cares so much for his students and is very passionate about he teaches! The lectures are never boring and you learn so many new things everyday! He is one of those professors that might even cause you to change your major. The workload wasn't that bad. When you get the chance, take this class!!

Quarter Taken: N/A Submitted March 31, 2010 Grade Received: N/A

This class is so hard that it builds a community from the students that have suffered through it. You will probably not meet everyone, but you will know who everyone is and who knows how to do the homework. I remember many nights of frantic phone-calls as people tried to get the correct solution to the preview or the problem sets.

It was a lot of work but it was also one of the best classes I have ever taken. Be warned; you may end up changing your major after the quarter is over.

Quarter Taken: N/A Submitted Nov. 22, 2008 Grade Received: N/A

Professor Lin is one of the best teachers I've ever had in my whole education experience. He is so dedicated to his students and provide them with help whenever they need it. Also, when I was in his Chem20AH class, he used to always bring us little treats (cookies and chocolates) that he bought from foreign countries. Once, he even bought the whole class pizza because we all did pretty well on our midterm. Besides spoiling his students, he also teaches very effectively. Some students may complain that he is very repetitive, but I think that his reviewing the materials is a good refresher for his students. His tests are not as hard as he say they are; as long as you study his derivations, then you'll be in good shape. Overall, I would recommend people to take his class.

Quarter Taken: N/A Submitted Dec. 15, 2008 Grade Received: N/A

Professor Lin's 20 AH class is by far one of the most difficult and time consuming classes offered to first year Science majors. The class requires about 12 hours a week of outside study along with 5 one-hour lectures every week. The course also requires high levels of understanding in math and physics. Although the course requires extensive studying and is often very frustrating, it is still manageable. Professor Lin offers review sessions and office hours that nearly the whole class goes to. Professor Lin is also very personable and cares a lot about the success of his students. He knows each of his students by name and is the only professor I have met so far who offers to write his students a letter of recommendation. If you make a genuine effort to learn the material, you will get an A or B!

Quarter Taken: N/A Submitted Dec. 20, 2005 Grade Received: N/A

Professor Lin is the nicest teacher I've had, and he rewards hard-working students well. Professor Lin spices up his lectures with anecdotes and interesting associations, as well. If you are willing to work hard and invest a lot of time in the class, you will do well and learn things you had never imagined you would.

During the first half of the course, or whenever we learned new material, I felt like I didn't understand anything. But I realized that this feeling came from the fact that quantum mechanics just does not rely on the classical mechanics we take for granted. The new material seeps in after a few weeks, and the class becomes understandable.

The class is pretty hard, but doable. You have to be willing to spend a LOT of time with the weekly problem sets, and there's some homework for the other days as well. Most of the latter can be solved relatively easily using the textbooks, and Professor Lin helps with the problem sets, giving hints during lectures and helping to solve problems during office hours, if needed.

I liked the fact that in the homework and the midterms/final, Professor Lin gave us the equations we had to use, and told us what to do with them! But let me emphasize, you still have to study a lot; before midterms/final, I felt like I was studying 24-7, which consists of looking over all your homework and the problems sets, mostly.

Quarter Taken: N/A Submitted Dec. 3, 2008 Grade Received: N/A

Perhaps one of the nicest teachers I have ever encountered. He bought all his students pizza, cookies from Japan, and cookies from San Francisco the day of lecture. In addition he is more than happy to stay after class for as long as you need him to to answer any questions about the lecture.
Although the material is difficult it is not impossible to master. He likes to give the impression, however, that his exams are nearly impossible when really they are not that difficult. Make sure to practice all the important derivations and to understand the origins of the formulas.
The professor also holds an inordinate number of office hours (and makes his ta's hold many office hours as well), one every day monday - friday and sometimes he even holds Saturday office hours (which are like 6 hours where he simply will let you ask him questions). Really devoted to his teaching and it's simply shocking how much he cares about his student progress.

Don't be misled, however, this class is not like a breeze, there are lots of rewards but it's a lot of work. He assigns one problem set a week as well as three shorter 1-2 question assignments. The shorter assignments can sometimes take a few minutes, but other times take hours as you get lost in an 'algebra jungle'. Beware that if you fall behind in the class you will suffer greatly.
Also, you have to go to lecture because the professor checks attendance (sort of) and you will most certainly fail if you don't follow him because none of the material he covers is really in the book.

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: 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!!

1 of 2


  • 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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