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elements Since ancient times, scientists and philosophers have attempted to discover, classify and synthesise the Earth’s elements. Now, thanks to the hard work of dedicated individuals, we have the periodic table: the ultimate guide to the elements, organised by atomic number and electron configuration. In the How It Works Book Of The Elements, we introduce you to the basics of elements and compounds, as well as taking a more in-depth look at the history of key discoveries. Every known element on the planet is covered in detail, from lanthanoids to actinoids, alkali metals to transition metals, and halogens to noble gases. You’ll find everything you need to know about the universe’s building blocks right here.
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The publisher cannot accept responsibility for any unsolicited material lost or damaged in the post. All text and layout is the copyright of Future Publishing Limited. Nothing in this bookazine may be reproduced in whole or part without the written permission of the publisher. All copyrights are recognised and used specifically for the purpose of criticism and review. Although the bookazine has endeavoured to ensure all information is correct at time of print, prices and availability may change. This bookazine is fully independent and not affiliated in any way with the companies mentioned herein. The content in this book appeared previously in the Carlton book The Definitive Illustrated Guide To The Elements
How it Works: Book of The Elements Sixth Edition Š 2017 Future Publishing Limited
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bookazine series
Contents 1
H Hydrogen Page 22
3
4
Li
Be
Lithium
Beryllium
Page 27
Page 35
11
12
Na
Mg
Sodium
Magnesium
Page 28
Page 36
19
20
Introduction.................................................................................................................................................................................... 8 Elements – a history.................................................................................................................................................... 16 Hydrogen........................................................................................................................................................................................22 Group 1 | The Alkali Metals .........................................................................................................................26 Group 2 | The Alkaline Earth Metals ........................................................................................... 34 D-block and the transition metals........................................................................................................ 44 Group 3 | The Transition Metals............................................................................................................ 46 Group 4 | The Transition Metals.............................................................................................................47 Group 5 | The Transition Metals.............................................................................................................52 Group 6 | The Transition Metals............................................................................................................ 58 Group 7 | The Transition Metals............................................................................................................ 63 Group 8 | The Transition Metals............................................................................................................ 66 Group 9 | The Transition Metals.............................................................................................................72 Group 10 | The Transition Metals.........................................................................................................75 Group 11 | The Transition Metals........................................................................................................ 80 Group 12 | The Transition Metals........................................................................................................ 86 F-block – the lanthanoids and the actinoids........................................................................ 92 The Lanthanoids................................................................................................................................................................94
d block 21
22
23
24
25
26
Fe
27
K
Ca
Sc
Ti
V
Cr
Mn
Co
Potassium
Calcium
Scandium
Titanium
Vanadium
Chromium
Manganese
Iron
Cobalt
Page 30
Page 38
Page 46
Page 47
Page 52
Page 58
Page 63
Page 66
Page 72
37
38
39
40
41
42
43
44
45
Rb
Sr
Y
Zr
Nb
Mo
Tc
Ru
Rh
Rubidium
Strontium
Yttrium
Zirconium
Niobium
Molybdenum
Technetium
Ruthium
Rhodium
Page 32
Page 41
Page 46
Page 50
Page 54
Page 60
Page 64
Page 70
Page 73
55
56
72
73
74
75
76
77
Cs
Ba
Hf
Ta
W
Re
Os
Ir
Caesium
Barium
Hafnium
Tantalum
Tungsten
Rhenium
Osmium
Iridium
Page 33
Page 42
Page 51
Page 56
Page 61
Page 65
Page 71
Page 74
87
88
104
105
1106
107
108
109
Fr
Ra
Rf
Db
Sg
Bh
Hs
Mt
Francium
Radium
Rutherfordium
Dubnium
Seaborgium
Bohrium
Hassium
Meltnerium
Page 33
Page 43
Page 169
Page 169
Page 169
Page 170
Page 170
Page 170
57
58
59
60
61
62
The Alkali Metals The Alkaline Earth Metals The Transition Metals The Post-Transition Metals Metalloids Other non-metals Halogens
Ce
Pr
Nd
Cerium
Praseodymium
Neodymium
Promethium
Pm Sm Samarium
Page 95
Page 96
Page 96
Page 96
Page 97
Page 97
89
90
91
92
93
94
Lanthanoids
Ac
Th
Pa
U
Np
Pu
Actinoids
Actinium
Thorium
Protactinium
Uranium
Neptunium
Plutonium
Transuranium elements
Page 103
Page 103
Page 103
Page 104
Page 165
Page 165
Noble gases
6
La Lanthanum
How It Works Book of The Elements
Contents The Actinoids...................................................................................................................................................................... 102 Group 13 | The Boron Group................................................................................................................... 106 Group 14 | The Carbon Group................................................................................................................ 112 Group 15 | The Nitrogen Group.......................................................................................................... 124 Group 16 | The Oxygen Group.............................................................................................................. 132 Group 17 | The Halogens............................................................................................................................... 144 Group 18 | The Noble Gases.................................................................................................................... 154 The Transuranium Elements................................................................................................................... 164 Index...................................................... 172 5 6 7 Credits..................................................174
B
29
Ni
Cu
30
Zn
N
He Helium Page 155
8
O
9
F
10
Ne
Boron
Carbon
Nitrogen
Oxygen
Fluorine
Neon
Page 107
Page 113
Page 125
Page 133
Page 145
Page 158
13
14
15
16
17
18
Al 28
C
2
Si
P
Aluminium
Silicon
Phosphorus
Sulfur
Chlorine
Argon
Page 108
Page 118
Page 128
Page 137
Page 148
Page 159
31
32
33
34
35
36
Ga
Ge
S
Cl
As
Se
Br
Ar Kr
Nickel
Copper
Zinc
Gallium
Germanium
Arsenic
Selenium
Bromine
Krypton
Page 76
Page 80
Page 86
Page 110
Page 120
Page 129
Page 140
Page 151
Page 161
46
47
48
49
50
51
52
53
54
Pd
Ag
Cd
In
Sn
Sb
Te
Palladium
Silver
Cadmium
Page 77
Page 82
Page 88
78
79
80
81
I
Xe
Indium
Tin
Antimony
Tellurium
Iodine
Xenon
Page 111
Page 120
Page 131
Page 142
Page 152
Page 162
82
83
84
85
86
Pt
Au
Hg
Tl
Pb
Bi
Po
At
Rn
Platinum
Gold
Mercury
Thallium
Lead
Bismuth
Polonium
Astatine
Radon
Page 78
Page 84
Page 89
Page 111
Page 121
Page 131
Page 143
Page 153
Page 163
110
111
112
113
114
115
116
117
118
Ds
Rg
Cn
Nh
Fl
Mc
Lv
Ts
Og
Darmstadium
Roentgenium
Copernicium
Nihonium
Flerovium
Moscovium
Livermorium
Tennessine
Oganesson
Page 170
Page 170
Page 170
Page 170
Page 170
Page 170
Page 170
Page 170
Page 170
65
66
67
68
69
70
71
f block 63
64
Eu
Gd
Tb
Dy
Ho
Er
Tm
Yb
Lu
Europium
Gadolinium
Terbium
Dysprosium
Holmium
Erbium
Thulium
Ytterbium
Lutetium
Page 97
Page 98
Page 98
Page 99
Page 99
Page 99
Page 99
Page 100
Page 101
95
96
97
98
99
100
101
102
103
Americium Page 167
Am Cm
Bk
Cf
Es
Fm Md
Curium
Berkelium
Californium
Einsteinium
Fermium
Page 167
Page 167
Page 167
Page 167
Page 167
No
Lr
Mendelevium
Nobelium
Lawrencium
Page 169
Page 169
Page 169
How It Works Book of The Elements
7
An introduction to the elements
An introduction to the elements “Modern physics and chemistry have reduced the complexity of the sensible world to an astonishing simplicity.” – Carl Sagan
Elements, compounds and mixtures Most familiar substances are mixtures or compounds. Wood, steel, air, salt, concrete, skin, water, plastics, glass, wax – these are all mixtures or compounds, made up of more than one element. We do encounter elements in our everyday life, albeit not completely pure. Gold and silver are good examples; and even in the purest sample of gold ever produced, one in every million atoms was an atom of an element other than gold. Copper (pipes), iron (railings), aluminium (foil) and carbon (as diamond) are further examples of elements we encounter in their fairly pure state. Some other elements are familiar simply because they are so important or commonplace. Oxygen, nitrogen, chlorine, calcium, sodium, lead – these are all examples of such elements. This book will explore the properties of all the elements. The properties of an element include its chemical behaviours – in other words, how its atoms interact with atoms of other elements. So for each element, we will also look at some important compounds and mixtures that contain it.
Please read! Sometimes, it makes little practical difference whether you read a book’s introduction or not. But that is not the case here. This introduction contains crucial information that will enable you to understand the organization of this book and the information it contains. It will also help you appreciate the complex beauty of the world – and how all of it can be explained by the interactions between only three types of particle: protons, neutrons and electrons. For it is a mind-boggling truth that from the core of our planet to the distant stars, all matter – be it solid, liquid, gas or plasma – is made of different combinations of just these three particles.
8
How It Works Book of The Elements
Protons, neutrons and electrons An atom has a diameter in the order of one ten-millionth of a millimetre (0.0000001 mm, 0.000000004 inches). An atom’s mass is concentrated in a heavy central part, the nucleus, made of protons and neutrons. The much lighter electrons surround the nucleus. Everything around you is made of only about 90 different types of atom: 90 different arrangements of protons, neutrons and electrons. These different types of atom are the elements. Protons carry positive electric charge; electrons carry a corresponding amount of negative electric charge. Scale them up in your imagination, so that they are little electrically charged balls you can hold in your hand, and you would feel them pulling towards each other because of their Proton, p+ mutual electrostatic attraction. Neutrons, as their name suggests, are neutral: they carry no electric charge. Hold a scaled-up one of these in your hand, and you will see that it is not Neutron, n attracted towards the proton or the electron.
Building atoms With these imaginary, scaled-up particles, we can start building atoms of the first few elements – beginning with the simplest and lightest element, hydrogen.
Electron, eAbove: Illustration of a proton (red), neutron (blue) and electron. The mass of a proton is the same as that of a neutron, more than 1,800 times that of an electron.
An introduction to the elements For the nucleus of your hydrogen atom, you just need a single, naked proton. To that, you will need to add your electron – by definition, an atom has equal numbers of protons and electrons, so that it has no charge overall. Hold the electron at some distance from the proton and the two particles will attract, as before. The force of attraction means that the electron has potential energy. Let go of the electron and it will “fall” towards the proton losing potential energy. You will notice that it stops short of crashing into the proton, and settles instead into an orbit around it. It is now in its lowest energy state.
Strange behaviours You have just built a hydrogen atom – albeit an imaginary one. There are a few strange things to notice, for the world of tiny particles is dominated by the weird laws of quantum physics. For example, as your electron fell towards your proton, you will have noticed that it did so in distinct jumps, rather than one smooth movement. For some reason that is built into the very fabric of the Universe, the electron is only “allowed” certain energies. The amount of energy the electron loses in each jump – the difference in energy between any two levels – is called a quantum. The lowest level of potential energy, which corresponds to the electron’s closest approach, is often written n=1. Every quantum of energy lost by an electron creates a burst of visible light or ultraviolet radiation, called a photon. Any two photons differ only in the amount of energy they possess. A photon of blue light has more energy than a photon of red light, and a photon of ultraviolet radiation has more energy than a photon of blue light. If you now knock your electron back up a few levels, watch it produce photons as it falls back. Some of the photons will be visible light, others will be invisible ultraviolet ones. Each element has a characteristic set of energy levels, since the exact levels are determined by the number of protons in the nucleus. And so, each element produces a characteristic set of photons of particular
Left: Discrete (separate and well-defined) lines in the visible part of the spectrum, produced by excited hydrogen atoms.
frequencies, which can be examined using a prism to separate the different frequencies into a spectrum consisting of bright lines on a dark background. As a consequence, elements can be identified by the colours of the light they give out when their electrons are given extra energy (excited) then allowed to settle down again. You can excite an electron with heat, electricity or by shining ultraviolet radiation on to it. Metal atoms will produce characteristic coloured light in the heat of a flame, for example – see page 27 for pictures of flame tests; and this process is responsible for the colours of fireworks, as electrons in metal atoms are repeatedly excited by the heat of combustion and then fall down to lower energies again. And in energy-saving fluorescent lamps, ultraviolet radiation excites electrons in atoms in the glass tube’s inner coating, producing red, green and blue photons that, when entering the eye together, give the illusion of white light.
Fuzzy orbitals You will have noticed another strange behaviour in your imaginary atom. Instead of being a welldefined particle, your electron appears as a fuzzy sphere surrounding the nucleus, called an orbital. The quantum world is an unfamiliar, probabilistic place, in which objects can be in more than one place at the same time and exist as spread-out waves as well as distinct particles. And so as well as being a well-defined particle, your electron is also a three-dimensional stationary wave of probability. The chemical properties of elements are determined mostly by the arrangement of electrons in orbitals around the nucleus.
Above: Illustration showing the distant electron energy levels around a hydrogen nucleus and around a beryllium nucleus (not to scale).
Atomic number Now move the electron away, leaving the naked proton again. To make the next element, with atomic number 2, you will have to add another proton to your nucleus. But all protons carry positive charge, so they strongly repel each other. What is worse, the closer they get, the more strongly they push apart.
Above: Illustration of an orbital, the region in which electrons can exist – as both a point particle and a spreadout wave.
How It Works Book of The Elements
9
An introduction to the elements
“This is the strong nuclear force – it is so strong that you will now have trouble pulling the proton and neutron apart” Fortunately, there is a solution. Put the second proton down for a moment and try adding a neutron instead. There is nothing stopping you this time, because the neutron has no electric charge. As you bring the neutron very close, you suddenly notice an incredibly strong force of attraction, pulling the neutron and proton together. This is the strong nuclear force – it is so strong that you will now have trouble pulling the proton and neutron apart. It only operates over an exceedingly short range. You now have a nucleus consisting of one proton (1p) and one neutron (1n). This is still hydrogen, since elements are defined by the number of protons in the nucleus – the atomic number. But this is a slightly different version of hydrogen, called hydrogen-2. The two versions are isotopes of hydrogen, and if you add another neutron, you will make another isotope, hydrogen-3. The strong nuclear force works with protons, too (but not electrons). If you can manage to push your other proton very close to your nucleus, the attractive strong nuclear force will overcome the repulsive force. The proton sticks after all, and your hydrogen-3 nucleus has become a nucleus of helium-4, with two protons and two neutrons (2p, 2n). This process of building heavier nuclei from lighter ones is called nuclear fusion.
Building elements Protons and neutrons were forced together in this Repulsive Forces (green arrows) between protons. The force is stronger the closer the protons are to each other
Attractive Force (orange line) is the strong nuclear force between proton and neutron
Strong nuclear force overcomes hydrogen-2 the repulsion between two protons
hydrogen-3
hydrogen-4
Above: Protons repel each other, and that repulsion increases the closer they are. But, at very small distances, the strong nuclear force holds protons and neutrons together, and can overcome that repulsion, building nuclei.
10
How It Works Book of The Elements
way in the intense heat and pressure in the first few minutes of the Universe, building helium-4 nucleus elements up to beryllium-8, which has 4 protons and 4 neutrons. All the other elements have been produced since then, by beryllium-8 nucleus nuclear fusion inside (two helium-4 nuclei) stars. For example, three helium-4 nuclei (2p, 2n) can fuse together to make a nucleus of carbon-12 (6p, 6n); add another helium-4 nucleus and carbon-12 nucleus (three helium-4 nuclei) you make oxygen-16 (8p, 8n), and so on. Various combinations are possible, and during its lifetime a typical star will produce all the elements up to iron, oxygen-16 nucleus (four helium-4 nuclei) which has atomic number 26, using only Above: Building larger hydrogen and helium as nuclei. Inside stars some of the most common elements starting ingredients. are formed by the fusion Elements with higher of helium-4 nuclei. Shown atomic numbers can here are beryllium-8, carbon-12 and oxygen-16 only be produced in supernovas – stars exploding at the end of their life cycle. So everything around you – and including you – is made of atoms that were built in the first few minutes of the Universe or inside stars and supernovas.
Electron shells To the helium-4 nucleus you made you will need two electrons if you want it to become a helium atom. Drop them in towards your new nucleus and you will find they both occupy the same spherical orbital around the nucleus – an s-orbital (the “s” has nothing to do with the word “spherical”). The two electrons are both at the same energy level, n=1, so this particular orbital is labelled 1s. Hydrogen has an electron configuration of 1s1; helium’s is 1s 2. As you build heavier elements, with more electrons, the outermost electrons will be further and further from the nucleus, as the innermost slots become filled up. An orbital can hold up to two electrons, so when it comes to the third element, lithium, a new
An introduction to the elements
s- and p-orbitals superimposed
Three p-orbitals Above: The three 2p orbitals, and an atom with s- and p-orbitals superimposed. In atoms with a filled outer shell, such as neon, the orbitals combine, forming a spherically-symmetrical orbital – such atoms are spheres.
orbital is needed. This second orbital is another spherical s-orbital, and it is at the next energy level, n=2, so it is labelled 2s. The electron configuration of lithium is 1s 2 2s1. If you look at the periodic table on page 5, you will see that lithium is in the second row, or period. The rows of the periodic table correspond to the energy levels in which you find an atom’s outermost electrons. So hydrogen and helium are in the first period because their electrons are at n=1. The Period 2 elements, from lithium to neon, have their outermost electrons at energy level n=2. Electrons that share the same energy level around the nucleus of an atom are said to be in the same shell. The electrons of hydrogen and helium can fit within the first shell (energy level n=1). At the second energy level – in the second shell – there is more space for electrons. A new type of orbital, the dumbbell-shaped p-orbital, makes its first appearance. Like an s-orbital, a p-orbital can hold up to two electrons. There are three p-orbitals, giving space for six electrons. So the second shell contains a total of eight electrons: two in s- and six in p-orbitals. Neon, at the end of Period 2, has the electron configuration 1s 2 2s 2 2p6, and has a filled outer shell; the element neon has an atomic number of 10. The third shell also has one s- and three p-orbitals, and so Period 3 of the periodic table holds another eight elements. By the end of the third period, we are up to element 18, argon, because the first three shells can contain 2, 8 and 8 electrons, respectively – a total of 18. In shell 4 (Period 4) a new type of orbital, the d-orbital, makes its first appearance, and by the sixth shell, electrons also have an f-orbital into which they can fall. In those shells where they exist, there are three p-orbitals, five d-orbitals and seven
“The nucleus would be extremely unstable and would fly apart in an instant” f-orbitals. Since each orbital can contain two electrons, there are a possible total of six p-electrons, 10 d-electrons and 14 f-electrons in each of the shells where they occur. Each set of orbitals is also known as a subshell; if you were building up an atom by adding electrons, as described above, and you had reached shell 4, the order of filling is: s-subshell first, then the d-subshell, then the p-subshell. Similarly, in the sixth shell, the order is s, d, f, p. The structure of the periodic table reflects this order; the s-block (Groups 1 and 2) corresponds to the s-subshell (just one orbital); the central block, called the d-block (Groups 3 to 12), corresponds to the d-subshell; the f-block, corresponding to the f-subshell, normally stands apart from the rest of the table, although it is included in the extended version of the table, after the d-block; and the right-hand section of the periodic table is the p-block (Groups 13 to 18), which corresponds to the p-subshell.
Unstable nuclei As we have been filling the electron shells, we should also have been adding protons to the nucleus, since the number of electrons in an atom is equal to the number of protons in the nucleus so that the atom has no overall electric charge. So by now, the nuclei are much bigger than that of hydrogen or helium. Argon, with its 18 electrons, must also have 18 protons in the nucleus. If a nucleus that big consisted only of protons, the protons’ mutual repulsion would overpower the attraction of the strong nuclear force. The nucleus would be extremely unstable and would fly apart in an instant. Neutrons provide the attractive strong nuclear force without adding the repulsive electrostatic force: they act like nuclear glue.
How It Works Book of The Elements
11
An introduction to the elements So, for example, the most common isotope of argon has 22 neutrons to help its 18 protons adhere. However, it is not always the case that more neutrons equals greater stability. Certain proton-neutron mixtures are more stable than others, and so for any element some isotopes are more common. The most common isotope of argon is argon-40, with an atomic mass of 40 (the mass of the electron is negligible, so the atomic mass is simply the total number of protons and neutrons). However, while argon-40 is by far the most common, there are other stable isotopes. The average atomic mass (the standard atomic weight) of any sample of argon atoms is not a whole number: it is 39.948. In fact, no element has a standard atomic weight that is a whole number; chlorine’s, for example, is 35.453. There are several things that can happen to an unstable nucleus. The two most common are alpha decay and beta decay. In alpha decay, a large and unstable nucleus expels a clump of two protons and two neutrons, called an alpha particle. The atomic number reduces by two, because the nucleus loses two protons. So, for example, a nucleus of radium-226 (88p, 138n) ejects an alpha particle to become a nucleus of radon-222 (86p, 136n). Alpha decay results in a transmutation of one element into another – in this case, radium becomes radon. This kind of nuclear instability is the reason why there are no more than about 90 naturallyoccurring elements. Any heavier ones that were made, in supernovas, have long since disintegrated to form lighter elements. Elements heavier than uranium, element 92, have only been made artificially, and most have only a fleeting existence. For more information on these transuranium elements, see p164–171. There are two elements with atomic number less than
uranium that also have no stable isotopes and are not found naturally: technetium and promethium. In beta decay, a neutron spontaneously changes into a proton and an electron. The electron is expelled from the nucleus at high speed, as a beta particle. This time, the atomic number increases by one, since there is now an extra proton in the nucleus. So, while argon-40 is stable, argon-41 (18p, 23n) is not; its nucleus undergoes beta decay to become a nucleus of potassium-41 (19p, 22n). Note how the mass of the nucleus is unchanged – because the new proton has the same mass as the old neutron – despite the fact that the element has transmuted. Alpha and beta decay are random processes, but in a sample of millions or billions the time for
Unstable nucleus increases its atomic number by one
fast electron (beta particle)
Above: Beta decay. A neutron in an unstable nucleus spontaneously turns into a proton and an electron. The atomic number increases by one because of the new proton.
half of them to decay is always the same; this is called the half-life. Nuclear reactions such as alpha and beta decay involve the nucleus losing energy. As a result, the nucleus emits a photon – just as electrons do when they drop down to a lower energy level. But the amount of energy involved in nuclear reactions is much greater, so they produce very energetic gamma ray photons rather than photons of visible light or ultraviolet radiation. The disintegration of nuclei, together with the alpha and beta particles and the gamma rays, constitute radioactivity.
Bonds Atoms – with their protons and neutrons in the nucleus and their electrons in orbitals around it – do not exist in isolation. This book alone is composed of countless trillions of them. If you start gathering many atoms of the same element Unstable nucleus reduces its atomic number by two
12
How It Works Book of The Elements
alpha particle
Left: Alphay decay. An unstable nucleus loses an alpha particle (2p, 2n), reducing its atomic number by two.