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Atomic Mass and Average Atomic Mass - Some Basic Concepts Of Chemistry #9

Apr 09, 2020
Hello, thank you for returning to my channel in this video, I am going to talk to you about

atomic

mass

and

average

atomic

mass

. Oh, suppose I'm standing in front of a mountain and I have this foot rule and I intend to find out. the height of the mountain, it would be possible for me to use the spittoon up and stop going up the mountain and while I go up, measure it with Fortune, it would be possible. The mountain is not thousands of feet high and using a foot ruler it is not either, my scale is correct.
atomic mass and average atomic mass   some basic concepts of chemistry 9
Neither the unit I am using is correct and the object I am measuring is too large to be measured with a unit like this. The opposite can also happen if we have atoms. Do you know that a hydrogen atom? weighs in grams weighs 1 point 6 7 3 6 to the power of 10 to the power of negative 24 grams, which means it's zero point zero zero zero there are 23 zeros and 1 6 7 3 6 grams is the mass of a hydrogen atom, what is which is extremely small, it is ridiculously small and therefore using the unit of gram for atoms is actually not practical because if you use grips it is unfathomable how small or the mass of an atom is therefore chemists In the 19th century they found a solution to this and assigned a special unit of measurement for the mass of atoms and this unit was called atomic mass unit.
atomic mass and average atomic mass   some basic concepts of chemistry 9

More Interesting Facts About,

atomic mass and average atomic mass some basic concepts of chemistry 9...

At that time there were no proper techniques to measure masses, so what did they do? They just measured mass relative to another mass, for example, understanding here and my friend is standing next to me and I weigh more than my friend. Well, my mass is greater than hers. There is a third friend who weighs even more than me, so her mass is even greater than mine. So obviously what happens to your mass for the Sprint? is more than the first friend, so when you have a fixed reference and you start comparing all the others with that, that's what chemists did, they took a hydrogen atom and assumed that a hydrogen atom would be assigned the marks of one unit of atomic mass why they took hydrogen because hydrogen is the lightest element and therefore they said there can't be a mass smaller than this and they said okay, hydrogen should have a mass of one unit of atomic mass but starting in 1961 scientists decided that hydrogen is a very unstable element and therefore using hydrogen as a reference is not a very good idea and there was also another factor: hydrogen is present as three isotopes: protium, deuterium and tritium have three masses, one two and three, and what happens if you get another one? atom and how you choose that the one you want is a h1 is protein, so what did they do?
atomic mass and average atomic mass   some basic concepts of chemistry 9
We now have better techniques for discovering mass and matter. Mass spectrometry was a technique that is used even today and through which the masses of atoms can be found with great precision, so what was decided in 1961 was that the reference would not be hydrogen, the reference it would be carbon and carbon has isotopes again, but it was decided that carbon 12 is the one we would talk about. It is used as a reference and today the carbon trace is used and as a reference and it is assumed that an atomic mass unit would be equal to 1 over 12 the mass of carbon 12 it was assumed that carbon 12 is the reference but the mass of the carbon 12 is not 1, the mass of carbon 12 is 12 and therefore an atomic mass unit would be 1 over 12 of carbon 12 amu.
atomic mass and average atomic mass   some basic concepts of chemistry 9
You know, in

chemistry

we always try to find shorter forms, so instead of MU it is now called unified mass and just the symbol. U is also used for atomic mass unit is the same means the same is 1 over 12 the mass of carbon was discovered what is the mass of carbon was discovered to be maha-mantra the mass of interest of carbon was found what was in grants one twelfth more, the mass of carbon in grams was calculated by mass spectrometry and was found to be equal to one point six six zero five 6 over 10 to the power of minus 24 grams this was the mass of a carbon atom an atomic mass unit that It was the mass of a point 12 the carbon atom 12 and as I told you but by mass spectrometry we also know that the mass of hydrogen in grams is one point six seven three six to the power of 10 to the power of minus 24 grams so yes I want to know which is the mass of hydrogen in atomic mass units.
What would we do? We take the mass of hydrogen in grams divided by the mass of an atomic mass unit in grams, that is, a unified mass in grams, so one point six seven. is the mass of hydrogen divided by the mass of one atomic mass unit would give us the number of atomic mass units, so it would be equal to one point zero zero seven eight EMU in other words, the hydrogen that was going to be one of you now agree according to the current reference standard is now equal to one point zero zero seven eight unified masses or atomic mass units similarly oxygen is according to this new system has a mass of 50 point 995 you in most your calculations in your eleventh and twelfth standards you would be using masses that are rounded up, we have generally used the mass of oxygen as 16 and hydrogen we still treat it as

some

thing that is done just to simplify your calculations, but otherwise, if made very precise calculations, he would do it.
We have to take into account these decimal places. Now this was the atomic mass and the units that we used, the atomic mass unit, we found the B. When we look at the periodic table, the atomic masses of the elements are given throughout the periodic table. table and all these masses are fractional, they are not zeros anywhere, we always point to

some

thing, so what is the ratio of these fractional masses? We can understand one of the reasons is that when you compare it with the atomic mass unit you may not get a whole number, for example, hydrogen does not get the mass, but it gets the mass of one point zero zero seven eight uma, so one of the reasons is this, but the other reason for the fractional masses of the atoms or elements in the periodic table is that we know in the previous video I told you when I was talking about the Deltans atomic theory I told you that isotopes exist and isotopes are atoms of the same element that have the same atomic number but different mass numbers in other words they have the same number of protons but the number of neutrons is different and, therefore, the number of protons decides the element, so if it is the same it means it is the same and in it, but if the mass is different, the neutrons are different than the sum of the two, which gives you the mass and therefore these atoms although they are the same element can have different masses so we take a natural sample of an element and find what is the percentage of the different isotopes of that element that are present in that natural sample and once you know that percentages You know one of the different isotopes and you know the exact mass in atomic mass units of that particular isotope, then we have to take into consideration all these percentages and the masses and find out the

average

of all of them, how do you find it? to get the average let's take this example here, this is a box and I put some color bonuses in the box, the blue walls weigh 40 grams each, the red balls are three and weigh 30 grams each and the green walls weigh 20 grams each. the blue ones are four, remember that the green and the red are three, three, in other words, I have ten balls in the box, how can I know the average atomic mass of these balls?
So, although they are all balls, let's say the ball is an element. So if they are all balls, it is one element, but their masses are different, then how can we know that the average of T is the mass and multiply it by the number o? Those balls plus 30 red balls to divide into three is my number plus twenty. green balls in what is the number of green balls 3 / number of bullets, this will give you 160 plus 92 61:10 which is 310 in 110, so this is equal to 31 grams, the average mass of the balls is 31 grams , so we do the same with the elements for example carbon is present in three nights atrophic forms carbon-12 carbon-13 and carbon-14 these are the relative abundances of these ninety-eight point eight nine two percent is the abundance of carbon-12 and the mass in a The muse of carbon 12 is 12.
Carbon 13 is present only 1.18 percent of a sample will be carbon 14 and the mass of it will be thirteen point zero zero three three five a. m., that's when you're comparing yourself to cover the trap, remember carbon? 14 is the third isotope and its abundance is very very low what is it in a sample of 100 molecules you will have 2 out of 10 to the power of minus 10 of those molecules would be carbon 14 and there must be 14 dot zero zero three one seven so how can we find the average atomic mass? 100 so what average atomic mass do you get the average atomic mass if you do this calculation it would be equal to twelve point zero one one this is how the mass of carbon was calculated and that is the mass that is indicated in the periodic table

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