1
00:00:01,920 --> 00:00:06,560
Speaker 1: Welcome to brain Stuff production of I Heart Radio. Hey,

2
00:00:06,640 --> 00:00:10,240
Speaker 1: brain Stuff, Laurin bobble bomb. Here. Atoms are the building

3
00:00:10,240 --> 00:00:13,480
Speaker 1: blocks of matter. Anything that has mass and occupies space

4
00:00:13,560 --> 00:00:16,640
Speaker 1: by having volume is made up of these we things

5
00:00:17,280 --> 00:00:19,560
Speaker 1: that goes for the air you breathe, the water you drink,

6
00:00:19,600 --> 00:00:23,759
Speaker 1: and your body itself. Isotopes are a vital concept in

7
00:00:23,760 --> 00:00:27,080
Speaker 1: the study of atoms and how they work. Chemists, physicists,

8
00:00:27,120 --> 00:00:29,480
Speaker 1: and geologists use them to make sense of our world.

9
00:00:29,960 --> 00:00:32,840
Speaker 1: But before we can explain what isotopes are or why

10
00:00:32,880 --> 00:00:35,240
Speaker 1: they're so important, we'll need to take a step back

11
00:00:35,280 --> 00:00:39,199
Speaker 1: and look at atoms as a whole. As you probably know,

12
00:00:39,479 --> 00:00:42,720
Speaker 1: atoms have three main components, two of which reside in

13
00:00:42,760 --> 00:00:45,880
Speaker 1: the atoms nucleus, located at the center of the atom.

14
00:00:45,960 --> 00:00:49,199
Speaker 1: The nucleus is a tightly packed cluster of particles. Some

15
00:00:49,280 --> 00:00:52,839
Speaker 1: of those particles are protons, which have positive electrical charges.

16
00:00:53,680 --> 00:00:57,280
Speaker 1: It's well documented that opposite charges attract, while similarly charged

17
00:00:57,320 --> 00:00:59,600
Speaker 1: bodies tend to repel one another. I think about the

18
00:00:59,680 --> 00:01:03,000
Speaker 1: ends of two magnets. So here's a question. How can

19
00:01:03,040 --> 00:01:06,200
Speaker 1: two or more protons with their positive charges come exist

20
00:01:06,280 --> 00:01:09,520
Speaker 1: in the same nucleus? Shouldn't they be pushing each other away.

21
00:01:10,160 --> 00:01:14,320
Speaker 1: That's where another type of particle comes in, neutrons. Neutrons

22
00:01:14,360 --> 00:01:18,480
Speaker 1: are subatomic particles that share nuclei with protons, but neutrons

23
00:01:18,520 --> 00:01:21,839
Speaker 1: don't possess an electrical charge. True to their name, neutrons

24
00:01:21,880 --> 00:01:26,000
Speaker 1: are neutral, being neither positively nor negatively charged. It's an

25
00:01:26,000 --> 00:01:30,120
Speaker 1: important attribute. By virtue of their neutrality, neutrons can stop

26
00:01:30,120 --> 00:01:33,280
Speaker 1: protons from driving one another clear out of the nucleus.

27
00:01:34,560 --> 00:01:38,240
Speaker 1: Orbiting the nucleus are the third main component of atoms, electrons,

28
00:01:38,319 --> 00:01:42,440
Speaker 1: which are ultra light particles with negative charges. Electrons facilitate

29
00:01:42,520 --> 00:01:45,240
Speaker 1: chemical bonding, and their movements can produce a little thing

30
00:01:45,280 --> 00:01:49,240
Speaker 1: called electricity. But protons are no less important for one thing,

31
00:01:49,320 --> 00:01:53,440
Speaker 1: they help scientists tell the elements apart. You might have

32
00:01:53,520 --> 00:01:56,320
Speaker 1: noticed that in most versions of the periodic table, each

33
00:01:56,400 --> 00:01:58,800
Speaker 1: square has a little number printed in its upper right

34
00:01:58,840 --> 00:02:02,320
Speaker 1: hand corner. That figure is known as the atomic number.

35
00:02:02,840 --> 00:02:04,920
Speaker 1: It tells the reader how many protons are in the

36
00:02:04,920 --> 00:02:09,280
Speaker 1: atomic nucleus of a given element. For example, Oxygen's atomic

37
00:02:09,360 --> 00:02:12,680
Speaker 1: number is eight. Every oxygen atom in the universe has

38
00:02:12,720 --> 00:02:16,160
Speaker 1: a nucleus with exactly eight protons, no more, no less.

39
00:02:17,360 --> 00:02:21,239
Speaker 1: Without this very specific arrangement of particles, oxygen wouldn't be oxygen.

40
00:02:21,840 --> 00:02:25,600
Speaker 1: Each elements atomic number, including oxygen's, is totally unique, and

41
00:02:25,680 --> 00:02:29,240
Speaker 1: it's a defining trait. No other element has eight protons

42
00:02:29,280 --> 00:02:33,400
Speaker 1: per nucleus. By counting the protons, you can identify an atom.

43
00:02:33,520 --> 00:02:36,639
Speaker 1: Just as oxygen atoms will always have eight protons, nitrogen

44
00:02:36,680 --> 00:02:41,240
Speaker 1: atoms invariably come with seven. It's that simple neutrons do

45
00:02:41,280 --> 00:02:44,320
Speaker 1: not follow suit the nucleus, and an oxygen atom is

46
00:02:44,320 --> 00:02:48,040
Speaker 1: guaranteed to harbor eight protons as we've established, However, it

47
00:02:48,120 --> 00:02:52,239
Speaker 1: might also contain anywhere from four to twenty neutrons. Isotopes

48
00:02:52,280 --> 00:02:55,160
Speaker 1: are variants of the same chemical element that have different

49
00:02:55,240 --> 00:02:59,400
Speaker 1: numbers of neutrons. Now, each isotope is named on the

50
00:02:59,440 --> 00:03:02,600
Speaker 1: basis its mass number, which is the total combined number

51
00:03:02,600 --> 00:03:06,200
Speaker 1: of neutrons and protons in an atom. For example, one

52
00:03:06,240 --> 00:03:09,200
Speaker 1: of the better known oxygen isotopes is called oxygen eighteen

53
00:03:09,480 --> 00:03:12,480
Speaker 1: because it's got the standard eight protons plus ten neutrons.

54
00:03:12,919 --> 00:03:16,600
Speaker 1: A related isotope, oxygen seventeen, has one fewer neutron in

55
00:03:16,639 --> 00:03:21,920
Speaker 1: the nucleus. Some combinations of subatomic particles are stronger than others.

56
00:03:22,280 --> 00:03:27,160
Speaker 1: Scientists classify oxygen seventeen and eighteen as stable isotopes. In

57
00:03:27,240 --> 00:03:30,160
Speaker 1: a stable isotope, the forces exerted by the protons and

58
00:03:30,200 --> 00:03:34,040
Speaker 1: neutrons hold each other together permanently, keeping the nucleus intact

59
00:03:35,480 --> 00:03:38,680
Speaker 1: on the flip side. The nuclei in radioactive isotopes, also

60
00:03:38,800 --> 00:03:42,640
Speaker 1: called radio isotopes, are unstable and will decay over time.

61
00:03:43,440 --> 00:03:47,720
Speaker 1: These things have a protons neutron ratio that's fundamentally unsustainable

62
00:03:47,760 --> 00:03:51,320
Speaker 1: in the long run. Nobody wants to stay in that predicament. Hence,

63
00:03:51,560 --> 00:03:55,400
Speaker 1: radioactive isotopes will shed some subatomic particles and release energy

64
00:03:55,440 --> 00:03:58,320
Speaker 1: while they're at it until they've converted themselves into nice

65
00:03:58,600 --> 00:04:03,800
Speaker 1: stable isotopes. So oxygen eighteen is stable, but oxygen nineteen

66
00:04:04,000 --> 00:04:07,520
Speaker 1: is not. The latter will inevitably break down and fast

67
00:04:07,760 --> 00:04:10,280
Speaker 1: within twenty six point eight eight seconds of its creation.

68
00:04:10,560 --> 00:04:13,920
Speaker 1: Any given sample of oxygen nineteen is guaranteed to lose

69
00:04:13,960 --> 00:04:17,320
Speaker 1: half of its atoms to the ravages of decay. That

70
00:04:17,360 --> 00:04:19,760
Speaker 1: means of oxygen nineteen has a half life of twenty

71
00:04:19,760 --> 00:04:22,400
Speaker 1: six point eight eight seconds. A half life is the

72
00:04:22,440 --> 00:04:26,200
Speaker 1: amount of time it takes of an isotope sample to decay.

73
00:04:26,560 --> 00:04:29,080
Speaker 1: Remember this concept, we're going to connect it to paleontology

74
00:04:29,120 --> 00:04:32,360
Speaker 1: in just a minute. But before we talk about fossil science,

75
00:04:32,520 --> 00:04:35,880
Speaker 1: there's an important point that needs to be made. Unlike oxygen,

76
00:04:36,080 --> 00:04:39,719
Speaker 1: some elements do not have any stable isotopes whatsoever. Consider

77
00:04:39,960 --> 00:04:43,240
Speaker 1: uranium in the natural world. There are three isotopes of

78
00:04:43,240 --> 00:04:46,440
Speaker 1: this heavy metal, and they're all radioactive. With the atomic

79
00:04:46,520 --> 00:04:50,039
Speaker 1: nuclei in a constant state of decay. Eventually a chunk

80
00:04:50,080 --> 00:04:53,800
Speaker 1: of uranium will turn into it altogether different element. Don't

81
00:04:53,839 --> 00:04:56,080
Speaker 1: bother trying to watch the transition in real time, though

82
00:04:56,279 --> 00:05:01,240
Speaker 1: the process unfolds very very slowly. Uranium two thirty eight,

83
00:05:01,279 --> 00:05:03,840
Speaker 1: the elements most common isotope, has a half life of

84
00:05:03,839 --> 00:05:08,159
Speaker 1: about four point five billion years. Gradually it will become

85
00:05:08,360 --> 00:05:12,360
Speaker 1: lead to OH six, which is stable. Likewise, uranium two

86
00:05:12,360 --> 00:05:14,960
Speaker 1: thirty five, with its seven hundred and four million year

87
00:05:15,000 --> 00:05:19,600
Speaker 1: half life, transitions into lead to OH seven, another stable isotope.

88
00:05:20,120 --> 00:05:24,520
Speaker 1: Two geologists, this is really useful information. Let's say somebody

89
00:05:24,560 --> 00:05:27,520
Speaker 1: finds a slab of rock whose zircon crystals contain a

90
00:05:27,560 --> 00:05:30,400
Speaker 1: mixture of uranium two thirty five and lead to OH seven.

91
00:05:30,880 --> 00:05:33,840
Speaker 1: The ratio of those two atoms can help scientists determine

92
00:05:33,920 --> 00:05:38,000
Speaker 1: the rocks age. Here's how Let's say the lead atoms

93
00:05:38,080 --> 00:05:41,719
Speaker 1: vastly outnumber their uranium counterparts. In that case, you know

94
00:05:41,760 --> 00:05:44,400
Speaker 1: you're looking at a pretty old rock. After all, the

95
00:05:44,480 --> 00:05:47,720
Speaker 1: uraniums had plenty of time to start transforming itself into lead.

96
00:05:48,560 --> 00:05:50,400
Speaker 1: On the other hand, if the opposite is true, and

97
00:05:50,440 --> 00:05:53,279
Speaker 1: the uranium atoms are more common, then the rock must

98
00:05:53,320 --> 00:05:57,120
Speaker 1: be on the younger side. The technique we've just described

99
00:05:57,160 --> 00:06:00,359
Speaker 1: is called radiometric dating. That's the act of using the

100
00:06:00,360 --> 00:06:03,599
Speaker 1: well documented decay rates of unstable isotopes to estimate the

101
00:06:03,640 --> 00:06:07,760
Speaker 1: age of rock samples and geologic formations. A Paleontologists have

102
00:06:07,800 --> 00:06:10,520
Speaker 1: harnessed the strategy to determine how much time has elapsed

103
00:06:10,600 --> 00:06:13,560
Speaker 1: since a particular fossil was deposited, though it's not always

104
00:06:13,600 --> 00:06:17,880
Speaker 1: possible to date the specimen directly. You don't need to

105
00:06:17,920 --> 00:06:21,720
Speaker 1: be a prehistory buff to appreciate isotopes. Medical practitioners use

106
00:06:21,760 --> 00:06:24,760
Speaker 1: some of the radioactive varieties to monitor blood flow, study

107
00:06:24,800 --> 00:06:28,360
Speaker 1: bone growth, and even fight cancer. Radio Isotopes have also

108
00:06:28,400 --> 00:06:32,480
Speaker 1: been used to give farmers insights into soil quality. So

109
00:06:32,720 --> 00:06:35,280
Speaker 1: there you have it. Something as seemingly abstract as the

110
00:06:35,360 --> 00:06:38,640
Speaker 1: variability of neutrons affects everything from cancer treatment to the

111
00:06:38,680 --> 00:06:47,560
Speaker 1: mysteries of deep time. Science is awesome. Today's episode was

112
00:06:47,560 --> 00:06:50,360
Speaker 1: written by Mark Mancini and produced by Tyler Clang. Brain

113
00:06:50,400 --> 00:06:52,719
Speaker 1: Stuff is a production of iHeart Radio's How Stuff Works.

114
00:06:52,920 --> 00:06:54,880
Speaker 1: For more on this and lots of other stable topics,

115
00:06:54,920 --> 00:06:57,480
Speaker 1: visit our home planet has Stuff Works dot com. And

116
00:06:57,560 --> 00:06:59,680
Speaker 1: for more podcasts on my heart radio, visit the eye

117
00:06:59,680 --> 00:07:02,280
Speaker 1: heart Rate app, Apple Podcasts, or wherever you listen to

118
00:07:02,320 --> 00:07:14,200
Speaker 1: your favorite shows. H