## Periodic Table

Science questions not covered in Chem 14A and 14B. Try to limit questions to chemistry (inorganic chemistry, physical chemistry, organic chemistry, biophysical chemistry, biochemistry, materials science, environmental chemistry).

Gillian Ward 1F
Posts: 61
Joined: Fri Sep 28, 2018 12:27 am

### Periodic Table

How should you round the atomic weights of the elements on the periodic table when using it for calculations and how many decimal places should you go out to?

Katie Sy 1L
Posts: 57
Joined: Fri Sep 28, 2018 12:18 am

### Re: Periodic Table

I tend to just use the whole number listed on the periodic table to make sure my answers are exact as possible, but if it's a super long number, I usually stop after 3 decimal places

Francis_Nguyen3D
Posts: 35
Joined: Fri Sep 28, 2018 12:24 am

### Re: Periodic Table

Typically, it is best not to round the atomic weights of the elements before using it for calculations because your final answer would not be as accurate as it could be. Usually, you would round at the end of your calculation depending on the amount of significant figures there are. You determine the amount of significant figures through the given/ starting amounts within the problem. Keep in mind, this also depends on the type of problem and how accurate you want your answer to be!

Vicky Lu 1L
Posts: 60
Joined: Fri Sep 28, 2018 12:18 am

### Re: Periodic Table

I tend to use the entirety of the atomic weight listed for that element on the periodic table. I only round at the very end for the final answer and that depends on how many significant figures are used in the given values that is stated at the very beginning from the question.

Aleeque Marselian 1A
Posts: 60
Joined: Fri Sep 28, 2018 12:24 am

### Re: Periodic Table

It is best to not round the atomic weight in order to produce a more accurate result, especially when having to conform to the appropriate number of significant figures. However, if the number is very long, I usually round to the nearest thousands place.

Ahmet_Dikyurt_3L
Posts: 35
Joined: Fri Sep 28, 2018 12:23 am

### Re: Periodic Table

Usually, the question or the previous questions should give you an idea of how much you should round. When I round, I look at the previous questions and if they rounded to the nearest hundredth than I round to the nearest hundredth. If they do it to the thousandth than I do it to the thousandth, and so on. Hope this helps :)

Megan Wong 4E
Posts: 32
Joined: Fri Sep 28, 2018 12:28 am

### Re: Periodic Table

I just had my discussion today, and my TA said to use the exact number on the periodic table that is given. For instance, if the periodic table provided says 12.011 for carbon, use that number rather than just 12.

vaishali 1D
Posts: 61
Joined: Fri Sep 28, 2018 12:19 am

### Re: Periodic Table

Gillian Ward 4H wrote:How should you round the atomic weights of the elements on the periodic table when using it for calculations and how many decimal places should you go out to?

I usually use the entire atomic weight given so that my final answer is more accurate than if I were to round from the start.

AJ Manzano 3K
Posts: 16
Joined: Fri Sep 28, 2018 12:25 am

### Re: Periodic Table

Use the full number given, as it typically cuts off at the thousandths place. Then round to the thousandths at the very end of your calculations.

Chris Freking 2G
Posts: 60
Joined: Fri Sep 28, 2018 12:29 am

### Re: Periodic Table

I will typically use the exact atomic weight listed on the periodic table and round my final answer if needed. Future problems should supposedly have given atomic weights

shouse1f
Posts: 63
Joined: Fri Sep 28, 2018 12:18 am

### Re: Periodic Table

I typically use the exact number written on the table and wait to round anything until the very end.

Grace Diaz 3F
Posts: 30
Joined: Fri Sep 28, 2018 12:24 am

### Re: Periodic Table

rounding atomic weight/mass can lead to small discrepancies so it's best not to do so until you've reached your answer. Usually I try to include at least three numbers after the decimal for accuracy when rounding to find the number of moles.

Brandon Sanchez 3J
Posts: 30
Joined: Wed Oct 03, 2018 12:16 am

### Re: Periodic Table

When rounding the atomic weights of elements, I believe it's best to round up to three decimal places to receive a more accurate answer than rounding up a whole answer and thus misleading your calculations.

Diana Chavez-Carrillo 2L
Posts: 122
Joined: Fri Sep 28, 2018 12:18 am

### Re: Periodic Table

It is best and safer to just keep the number exactly as seen on the periodic table so that you do not round too much. Usually you do the rounding until the very end of your calculations.

Anna O 2C
Posts: 98
Joined: Fri Sep 28, 2018 12:19 am

### Re: Periodic Table

The safest way to prevent incorrect rounding early on is to use the entirety of the number given on the periodic table. With other pieces of data, rounding is more difficult to fully avoid, but avoiding rounding with Periodic elements will produce the most accurate answer possible, and then it can be rounded to the lowest amount of significant figures given in the question.

Arlene Linares 3A
Posts: 50
Joined: Fri Sep 28, 2018 12:25 am

### Re: Periodic Table

Katie Sy 1J wrote:I tend to just use the whole number listed on the periodic table to make sure my answers are exact as possible, but if it's a super long number, I usually stop after 3 decimal places

That's helpful to know thank you

505211599
Posts: 60
Joined: Fri Sep 28, 2018 12:28 am

### Re: Periodic Table

I typically try to round to as many decimal places that would allow for an accurate answer but also allows for the limiting significant figure to determine the answer.