[Script Info]
Title: 
[Events]
Format: Layer, Start, End, Style, Name, MarginL, MarginR, MarginV, Effect, Text
Dialogue: 0,0:00:01.68,0:00:05.28,Default,,0000,0000,0000,,So the atomic number is symbolized by Z
Dialogue: 0,0:00:05.28,0:00:09.10,Default,,0000,0000,0000,,and it refers to the number of protons in a nucleus.
Dialogue: 0,0:00:09.10,0:00:11.62,Default,,0000,0000,0000,,And you can find the atomic number on the periodic table.
Dialogue: 0,0:00:11.62,0:00:14.33,Default,,0000,0000,0000,,So we're going to talk about hydrogen in this video.
Dialogue: 0,0:00:14.33,0:00:17.82,Default,,0000,0000,0000,,So for hydrogen, hydrogen's atomic number is one.
Dialogue: 0,0:00:17.82,0:00:19.93,Default,,0000,0000,0000,,So it's right here, so there's one proton
Dialogue: 0,0:00:19.93,0:00:22.13,Default,,0000,0000,0000,,in the nucleus of a hydrogen atom.
Dialogue: 0,0:00:22.13,0:00:26.02,Default,,0000,0000,0000,,In a neutral atom, the number of protons
Dialogue: 0,0:00:26.02,0:00:29.32,Default,,0000,0000,0000,,is equal to the number of electrons,
Dialogue: 0,0:00:29.32,0:00:31.11,Default,,0000,0000,0000,,because in a neutral atom there's
Dialogue: 0,0:00:31.11,0:00:32.93,Default,,0000,0000,0000,,no overall charge and the positive charges
Dialogue: 0,0:00:32.93,0:00:35.62,Default,,0000,0000,0000,,of the protons completely balance
Dialogue: 0,0:00:35.62,0:00:39.11,Default,,0000,0000,0000,,with the negative charges of the electrons.
Dialogue: 0,0:00:39.11,0:00:42.57,Default,,0000,0000,0000,,So let's go ahead and draw an atom of hydrogen.
Dialogue: 0,0:00:42.57,0:00:45.07,Default,,0000,0000,0000,,We know the atomic number of hydrogen is one,
Dialogue: 0,0:00:45.07,0:00:47.46,Default,,0000,0000,0000,,so there's one proton in the nucleus.
Dialogue: 0,0:00:47.46,0:00:50.95,Default,,0000,0000,0000,,So there's my one proton in the nucleus, and we're talking
Dialogue: 0,0:00:50.95,0:00:53.74,Default,,0000,0000,0000,,about a neutral hydrogen atom, so there's one electron.
Dialogue: 0,0:00:53.74,0:00:55.50,Default,,0000,0000,0000,,I'm going to draw that one electron
Dialogue: 0,0:00:55.50,0:00:57.69,Default,,0000,0000,0000,,somewhere outside the nucleus and I'm going
Dialogue: 0,0:00:57.69,0:01:00.25,Default,,0000,0000,0000,,to use the oversimplified Bohr model.
Dialogue: 0,0:01:00.25,0:01:02.41,Default,,0000,0000,0000,,So this isn't actually what an atom looks like,
Dialogue: 0,0:01:02.41,0:01:05.23,Default,,0000,0000,0000,,but it's a very simply view that helps you get started.
Dialogue: 0,0:01:05.23,0:01:10.43,Default,,0000,0000,0000,,So this is one, this one version of hydrogen.
Dialogue: 0,0:01:10.43,0:01:13.17,Default,,0000,0000,0000,,This is one isotope of hydrogen.
Dialogue: 0,0:01:13.25,0:01:15.03,Default,,0000,0000,0000,,So this is called protium.
Dialogue: 0,0:01:15.04,0:01:16.93,Default,,0000,0000,0000,,Let me go ahead and write that here.
Dialogue: 0,0:01:16.93,0:01:19.47,Default,,0000,0000,0000,,So this is protium and let's talk about isotopes.
Dialogue: 0,0:01:19.51,0:01:22.84,Default,,0000,0000,0000,,An isotope, isotopes are atoms of a single element.
Dialogue: 0,0:01:22.91,0:01:25.38,Default,,0000,0000,0000,,So we're talking about hydrogen here.
Dialogue: 0,0:01:25.43,0:01:30.41,Default,,0000,0000,0000,,That differ in the number of neutrons in their nuclei.
Dialogue: 0,0:01:30.41,0:01:33.64,Default,,0000,0000,0000,,So let's talk about the next isotope of hydrogen.
Dialogue: 0,0:01:33.65,0:01:35.75,Default,,0000,0000,0000,,So this is called deuteriums.
Dialogue: 0,0:01:35.75,0:01:38.56,Default,,0000,0000,0000,,Let me go ahead and write deuterium here.
Dialogue: 0,0:01:38.56,0:01:43.30,Default,,0000,0000,0000,,Deuterium is hydrogen, so it must have one proton
Dialogue: 0,0:01:43.33,0:01:47.33,Default,,0000,0000,0000,,in the nucleus and it must have one electron outside
Dialogue: 0,0:01:47.37,0:01:50.12,Default,,0000,0000,0000,,the nucleus, but if you look at the definition
Dialogue: 0,0:01:50.12,0:01:53.22,Default,,0000,0000,0000,,for isotopes, atoms of a single element that differ
Dialogue: 0,0:01:53.22,0:01:56.84,Default,,0000,0000,0000,,in the number of neutrons, protium has zero
Dialogue: 0,0:01:56.84,0:01:59.35,Default,,0000,0000,0000,,neutrons in the nucleus.
Dialogue: 0,0:01:59.35,0:02:00.92,Default,,0000,0000,0000,,Deuterium has one.
Dialogue: 0,0:02:00.92,0:02:03.81,Default,,0000,0000,0000,,So let me go ahead and draw in deuterium's one neutron.
Dialogue: 0,0:02:03.81,0:02:07.27,Default,,0000,0000,0000,,I'll use blue here, so neutrons are going to be blue.
Dialogue: 0,0:02:07.27,0:02:11.52,Default,,0000,0000,0000,,So deuterium has one neutron and since neutrons have mass,
Dialogue: 0,0:02:11.52,0:02:14.29,Default,,0000,0000,0000,,deuterium has more mass than protium.
Dialogue: 0,0:02:14.29,0:02:17.27,Default,,0000,0000,0000,,So isotopes have different masses because they differ
Dialogue: 0,0:02:17.27,0:02:19.15,Default,,0000,0000,0000,,in terms of number of neutrons.
Dialogue: 0,0:02:19.15,0:02:21.96,Default,,0000,0000,0000,,Notice though, that they have the same atomic number,
Dialogue: 0,0:02:21.97,0:02:24.74,Default,,0000,0000,0000,,they have the same number of protons in the nucleus.
Dialogue: 0,0:02:24.74,0:02:26.81,Default,,0000,0000,0000,,Right, it's one proton in the nucleus.
Dialogue: 0,0:02:26.81,0:02:28.31,Default,,0000,0000,0000,,And that's important because if you change
Dialogue: 0,0:02:28.31,0:02:29.99,Default,,0000,0000,0000,,the number of protons, you're changing the element,
Dialogue: 0,0:02:29.99,0:02:32.75,Default,,0000,0000,0000,,and that's not what we're doing here.
Dialogue: 0,0:02:32.75,0:02:34.97,Default,,0000,0000,0000,,We're talking about atoms of a single element.
Dialogue: 0,0:02:34.97,0:02:38.02,Default,,0000,0000,0000,,Deuterium is still hydrogen, it's an isotope.
Dialogue: 0,0:02:38.02,0:02:41.19,Default,,0000,0000,0000,,Finally, our last isotope, which is tridium.
Dialogue: 0,0:02:41.19,0:02:45.29,Default,,0000,0000,0000,,So tritium has one proton in the nucleus,
Dialogue: 0,0:02:45.29,0:02:48.13,Default,,0000,0000,0000,,one electron outside the nucleus, and we draw
Dialogue: 0,0:02:48.13,0:02:51.29,Default,,0000,0000,0000,,that in here, and it must differ in terms
Dialogue: 0,0:02:51.29,0:02:55.65,Default,,0000,0000,0000,,of number of neutrons, so tritium has two neutrons.
Dialogue: 0,0:02:55.65,0:02:57.84,Default,,0000,0000,0000,,Let me go ahead and draw the two
Dialogue: 0,0:02:57.84,0:02:59.97,Default,,0000,0000,0000,,neutrons here in the nucleus.
Dialogue: 0,0:02:59.97,0:03:03.27,Default,,0000,0000,0000,,And so those are the isotopes of hydrogen.
Dialogue: 0,0:03:03.27,0:03:07.46,Default,,0000,0000,0000,,How do we distinguish between the different isotopes?
Dialogue: 0,0:03:07.46,0:03:10.24,Default,,0000,0000,0000,,Well we're going to write little symbols
Dialogue: 0,0:03:10.24,0:03:13.00,Default,,0000,0000,0000,,to represent these isotopes.
Dialogue: 0,0:03:13.00,0:03:15.63,Default,,0000,0000,0000,,And so the symbol that we'll draw here
Dialogue: 0,0:03:15.63,0:03:18.62,Default,,0000,0000,0000,,for protium is going to have the element symbol,
Dialogue: 0,0:03:18.62,0:03:21.47,Default,,0000,0000,0000,,which is, of course, hydrogen, and then down here
Dialogue: 0,0:03:21.47,0:03:24.38,Default,,0000,0000,0000,,we're going to write the atomic number.
Dialogue: 0,0:03:24.38,0:03:27.73,Default,,0000,0000,0000,,So the subscript is the atomic number which is one,
Dialogue: 0,0:03:27.73,0:03:30.47,Default,,0000,0000,0000,,because there's one proton in the nucleus,
Dialogue: 0,0:03:30.47,0:03:33.25,Default,,0000,0000,0000,,and then for the superscript, we're going
Dialogue: 0,0:03:33.25,0:03:35.94,Default,,0000,0000,0000,,to write in the mass number.
Dialogue: 0,0:03:35.94,0:03:38.24,Default,,0000,0000,0000,,So let me move down here so we can look
Dialogue: 0,0:03:38.24,0:03:40.20,Default,,0000,0000,0000,,at the definition for the mass number.
Dialogue: 0,0:03:40.20,0:03:42.51,Default,,0000,0000,0000,,The mass number is the combined number
Dialogue: 0,0:03:42.51,0:03:45.69,Default,,0000,0000,0000,,of protons and neutrons in a nucleus,
Dialogue: 0,0:03:45.69,0:03:51.11,Default,,0000,0000,0000,,so it's protons and neutrons, and it's symbolized by A.
Dialogue: 0,0:03:51.11,0:03:53.42,Default,,0000,0000,0000,,So A is the mass number, which is equal
Dialogue: 0,0:03:53.42,0:03:56.55,Default,,0000,0000,0000,,to the number of protons, that's the atomic
Dialogue: 0,0:03:56.55,0:03:58.83,Default,,0000,0000,0000,,number which we symbolized by Z,
Dialogue: 0,0:03:58.83,0:04:01.44,Default,,0000,0000,0000,,plus the number of neutrons.
Dialogue: 0,0:04:01.44,0:04:05.10,Default,,0000,0000,0000,,So A is equal to Z plus N.
Dialogue: 0,0:04:05.10,0:04:08.53,Default,,0000,0000,0000,,And for protium, let's look at protium here.
Dialogue: 0,0:04:08.53,0:04:12.30,Default,,0000,0000,0000,,So in the nucleus there's only one proton
Dialogue: 0,0:04:12.30,0:04:15.06,Default,,0000,0000,0000,,and zero neutrons, so one plus zero
Dialogue: 0,0:04:15.06,0:04:18.32,Default,,0000,0000,0000,,gives us a mass number of one.
Dialogue: 0,0:04:18.32,0:04:21.47,Default,,0000,0000,0000,,And I'll use red here for mass number so we can distinguish.
Dialogue: 0,0:04:21.47,0:04:25.26,Default,,0000,0000,0000,,Alright, so mass number is red and let me use
Dialogue: 0,0:04:25.26,0:04:31.01,Default,,0000,0000,0000,,a different color here for the atomic number.
Dialogue: 0,0:04:31.01,0:04:33.45,Default,,0000,0000,0000,,Let me use magenta here.
Dialogue: 0,0:04:33.45,0:04:36.53,Default,,0000,0000,0000,,So the subscript is the atomic number
Dialogue: 0,0:04:36.53,0:04:39.83,Default,,0000,0000,0000,,and that's Z, and the superscript
Dialogue: 0,0:04:39.83,0:04:43.92,Default,,0000,0000,0000,,is the mass number and that's A.
Dialogue: 0,0:04:43.92,0:04:47.45,Default,,0000,0000,0000,,So this symbol represents the protium isotope.
Dialogue: 0,0:04:47.45,0:04:50.74,Default,,0000,0000,0000,,Let's draw one for deuterium.
Dialogue: 0,0:04:50.74,0:04:52.89,Default,,0000,0000,0000,,So it's hydrogen so we put an H here.
Dialogue: 0,0:04:52.89,0:04:56.71,Default,,0000,0000,0000,,There is still one proton in the nucleus,
Dialogue: 0,0:04:56.71,0:04:58.23,Default,,0000,0000,0000,,right one proton in the nucleus,
Dialogue: 0,0:04:58.23,0:05:00.58,Default,,0000,0000,0000,,so we put an atomic number of one.
Dialogue: 0,0:05:00.58,0:05:02.75,Default,,0000,0000,0000,,The mass number is the superscript,
Dialogue: 0,0:05:02.75,0:05:05.99,Default,,0000,0000,0000,,it's the combined number of protons and neutrons.
Dialogue: 0,0:05:05.99,0:05:07.33,Default,,0000,0000,0000,,So we look in the nucleus here.
Dialogue: 0,0:05:07.33,0:05:08.63,Default,,0000,0000,0000,,There's one proton and one neutron.
Dialogue: 0,0:05:08.63,0:05:12.06,Default,,0000,0000,0000,,So one plus one is equal to two.
Dialogue: 0,0:05:12.06,0:05:14.65,Default,,0000,0000,0000,,So we put a two here for the superscript.
Dialogue: 0,0:05:14.65,0:05:17.26,Default,,0000,0000,0000,,And finally for tritium, it's still hydrogen.
Dialogue: 0,0:05:17.26,0:05:20.19,Default,,0000,0000,0000,,So we put hydrogen here.
Dialogue: 0,0:05:20.19,0:05:24.01,Default,,0000,0000,0000,,There's one proton in the nucleus,
Dialogue: 0,0:05:24.01,0:05:26.87,Default,,0000,0000,0000,,atomic number of one, so we put a one here.
Dialogue: 0,0:05:26.87,0:05:29.70,Default,,0000,0000,0000,,And then the combined numbers of protons
Dialogue: 0,0:05:29.70,0:05:32.39,Default,,0000,0000,0000,,and neutrons, that would be three.
Dialogue: 0,0:05:32.39,0:05:37.33,Default,,0000,0000,0000,,So one proton plus two neutrons gives us three.
Dialogue: 0,0:05:37.33,0:05:39.46,Default,,0000,0000,0000,,So there's the symbol for tritium.
Dialogue: 0,0:05:39.46,0:05:42.70,Default,,0000,0000,0000,,So here are the isotopes of hydrogen
Dialogue: 0,0:05:42.70,0:05:44.95,Default,,0000,0000,0000,,and using these symbols allows us
Dialogue: 0,0:05:44.95,0:05:47.21,Default,,0000,0000,0000,,to differentiate between them.
Dialogue: 0,0:05:47.21,0:05:49.98,Default,,0000,0000,0000,,So let's take what we've learned
Dialogue: 0,0:05:49.98,0:05:53.48,Default,,0000,0000,0000,,and do a few more practice problems here.
Dialogue: 0,0:05:53.48,0:05:56.85,Default,,0000,0000,0000,,So let's look at a symbol for carbon.
Dialogue: 0,0:05:56.85,0:06:02.76,Default,,0000,0000,0000,,So here we have carbon with subscript six, superscript 12.
Dialogue: 0,0:06:02.76,0:06:05.53,Default,,0000,0000,0000,,And if we want to know how many protons,
Dialogue: 0,0:06:05.53,0:06:08.27,Default,,0000,0000,0000,,electrons and neutrons there are.
Dialogue: 0,0:06:08.27,0:06:10.28,Default,,0000,0000,0000,,So let's first think about protons.
Dialogue: 0,0:06:10.28,0:06:12.09,Default,,0000,0000,0000,,Well we know that the subscript is
Dialogue: 0,0:06:12.09,0:06:14.26,Default,,0000,0000,0000,,the atomic number and the atomic number is
Dialogue: 0,0:06:14.26,0:06:16.28,Default,,0000,0000,0000,,equal to the number of protons.
Dialogue: 0,0:06:16.28,0:06:21.13,Default,,0000,0000,0000,,So there are six protons in this atom of carbon.
Dialogue: 0,0:06:21.13,0:06:23.92,Default,,0000,0000,0000,,And if it's a neutral atom of carbon, the number
Dialogue: 0,0:06:23.92,0:06:27.74,Default,,0000,0000,0000,,of electrons must be equal to the number of protons.
Dialogue: 0,0:06:27.74,0:06:29.80,Default,,0000,0000,0000,,So if there are six protons, there
Dialogue: 0,0:06:29.80,0:06:32.32,Default,,0000,0000,0000,,must also be six electrons.
Dialogue: 0,0:06:32.32,0:06:36.61,Default,,0000,0000,0000,,And finally, how do we figure out the number of neutrons?
Dialogue: 0,0:06:36.61,0:06:40.90,Default,,0000,0000,0000,,Well let's go ahead and write down the formula we discussed.
Dialogue: 0,0:06:40.90,0:06:43.72,Default,,0000,0000,0000,,The mass number is equal to the atomic
Dialogue: 0,0:06:43.72,0:06:47.50,Default,,0000,0000,0000,,number plus the number of neutrons.
Dialogue: 0,0:06:47.50,0:06:53.61,Default,,0000,0000,0000,,So the mass number was right here, that's 12.
Dialogue: 0,0:06:53.61,0:06:55.29,Default,,0000,0000,0000,,So we can put in a 12.
Dialogue: 0,0:06:55.29,0:06:59.02,Default,,0000,0000,0000,,The atomic number was six, right here.
Dialogue: 0,0:06:59.02,0:07:00.68,Default,,0000,0000,0000,,So we put in a six.
Dialogue: 0,0:07:00.68,0:07:03.17,Default,,0000,0000,0000,,Plus the number of neutrons.
Dialogue: 0,0:07:03.17,0:07:04.79,Default,,0000,0000,0000,,Plus the number of neutrons.
Dialogue: 0,0:07:04.79,0:07:06.73,Default,,0000,0000,0000,,So the number of neutrons is just equal to
Dialogue: 0,0:07:06.73,0:07:10.01,Default,,0000,0000,0000,,12 minus six, which is, of course, six.
Dialogue: 0,0:07:10.01,0:07:11.48,Default,,0000,0000,0000,,So there are six neutrons.
Dialogue: 0,0:07:11.48,0:07:14.60,Default,,0000,0000,0000,,So just subtract the atomic number
Dialogue: 0,0:07:14.60,0:07:16.92,Default,,0000,0000,0000,,from the mass number and you'll get
Dialogue: 0,0:07:16.92,0:07:19.46,Default,,0000,0000,0000,,the number of neutrons in your atom.
Dialogue: 0,0:07:19.46,0:07:21.46,Default,,0000,0000,0000,,Let's do another one.
Dialogue: 0,0:07:21.46,0:07:27.69,Default,,0000,0000,0000,,This is carbon and this time we have a superscript of 13.
Dialogue: 0,0:07:27.69,0:07:30.14,Default,,0000,0000,0000,,The atomic number doesn't change
Dialogue: 0,0:07:30.14,0:07:32.74,Default,,0000,0000,0000,,when you're talking about an isotope.
Dialogue: 0,0:07:32.74,0:07:34.26,Default,,0000,0000,0000,,If you change the atomic number,
Dialogue: 0,0:07:34.26,0:07:35.77,Default,,0000,0000,0000,,you change the element.
Dialogue: 0,0:07:35.77,0:07:39.27,Default,,0000,0000,0000,,So there's still six protons in the nucleus
Dialogue: 0,0:07:39.27,0:07:42.14,Default,,0000,0000,0000,,of this atom and in a neutral atom,
Dialogue: 0,0:07:42.14,0:07:45.19,Default,,0000,0000,0000,,there must be the equal number of electrons.
Dialogue: 0,0:07:45.19,0:07:47.81,Default,,0000,0000,0000,,So six electrons and then finally,
Dialogue: 0,0:07:47.81,0:07:50.00,Default,,0000,0000,0000,,how many neutrons are there?
Dialogue: 0,0:07:50.00,0:07:53.06,Default,,0000,0000,0000,,Well just like we did before, we subtract
Dialogue: 0,0:07:53.06,0:07:57.51,Default,,0000,0000,0000,,the atomic number from the mass number.
Dialogue: 0,0:07:57.51,0:08:03.24,Default,,0000,0000,0000,,So we just have to 13 minus six
Dialogue: 0,0:08:03.24,0:08:05.16,Default,,0000,0000,0000,,to figure out the number of neutrons.
Dialogue: 0,0:08:05.16,0:08:07.93,Default,,0000,0000,0000,,So 13 minus six is, of course, seven.
Dialogue: 0,0:08:07.93,0:08:11.58,Default,,0000,0000,0000,,So there are seven neutrons in this atom.
Dialogue: 0,0:08:11.58,0:08:15.37,Default,,0000,0000,0000,,Another way to represent isotopes,
Dialogue: 0,0:08:15.37,0:08:17.72,Default,,0000,0000,0000,,let's say we wanted to represent this isotope
Dialogue: 0,0:08:17.72,0:08:19.60,Default,,0000,0000,0000,,in a different way, sometimes you'll see it
Dialogue: 0,0:08:19.60,0:08:21.60,Default,,0000,0000,0000,,where you write the name of the element.
Dialogue: 0,0:08:21.60,0:08:23.16,Default,,0000,0000,0000,,So this is carbon.
Dialogue: 0,0:08:23.16,0:08:24.83,Default,,0000,0000,0000,,And then you put a hyphen here
Dialogue: 0,0:08:24.83,0:08:26.40,Default,,0000,0000,0000,,and then you put the mass number.
Dialogue: 0,0:08:26.40,0:08:30.67,Default,,0000,0000,0000,,So carbon hyphen 13 refers to this isotope
Dialogue: 0,0:08:30.67,0:08:34.17,Default,,0000,0000,0000,,of carbon and this is called hyphen notation.
Dialogue: 0,0:08:34.17,0:08:38.89,Default,,0000,0000,0000,,So let me go ahead and write this hyphen notation.
Dialogue: 0,0:08:38.89,0:08:42.81,Default,,0000,0000,0000,,Alright, let's do one more example here.
Dialogue: 0,0:08:42.81,0:08:45.47,Default,,0000,0000,0000,,Let's do one that looks a little bit scarier.
Dialogue: 0,0:08:45.47,0:08:48.46,Default,,0000,0000,0000,,So let's do uranium.
Dialogue: 0,0:08:48.46,0:08:50.22,Default,,0000,0000,0000,,So U is uranium.
Dialogue: 0,0:08:50.22,0:08:52.95,Default,,0000,0000,0000,,The atomic number of uranium is 92.
Dialogue: 0,0:08:52.95,0:08:56.97,Default,,0000,0000,0000,,The mass number for this isotope is 235.
Dialogue: 0,0:08:56.97,0:08:59.14,Default,,0000,0000,0000,,So how many protons, electrons,
Dialogue: 0,0:08:59.14,0:09:02.98,Default,,0000,0000,0000,,and neutrons in this atom of uranium?
Dialogue: 0,0:09:02.98,0:09:05.40,Default,,0000,0000,0000,,So once again for protons, we look
Dialogue: 0,0:09:05.40,0:09:07.80,Default,,0000,0000,0000,,at the atomic number, that's 92.
Dialogue: 0,0:09:07.80,0:09:11.76,Default,,0000,0000,0000,,So there must be 92 protons.
Dialogue: 0,0:09:11.76,0:09:15.07,Default,,0000,0000,0000,,In a neutral atom, the number of electrons is equal
Dialogue: 0,0:09:15.07,0:09:16.44,Default,,0000,0000,0000,,to the number of protons.
Dialogue: 0,0:09:16.44,0:09:19.13,Default,,0000,0000,0000,,So there are 92 electrons and then finally,
Dialogue: 0,0:09:19.13,0:09:21.15,Default,,0000,0000,0000,,to figure out the number of neutrons,
Dialogue: 0,0:09:21.15,0:09:26.53,Default,,0000,0000,0000,,we subtract this number from the mass number.
Dialogue: 0,0:09:26.53,0:09:34.15,Default,,0000,0000,0000,,So we just need to do 235 minus 92.
Dialogue: 0,0:09:34.15,0:09:37.88,Default,,0000,0000,0000,,And that gives us 143.
Dialogue: 0,0:09:37.88,0:09:43.66,Default,,0000,0000,0000,,So there are 143 neutrons.