30-Second Elements E-Book

Eric Scerri

• Herausgeber: Icon Books
• Kategorie: Wissenschaft und neue Technologien
• Serie: 30-Second
• Sprache: Englisch

Seitenzahl: 155

Veröffentlichungsjahr: 2013

Beschreibung

When was radium discovered? Who are Dmitri Mendeleev and Glenn T. Seaborg? Who discovered uranium's radioactivity? Which element is useful for dating the age of Earth? And why doesn't gold have a scientific name? 30-Second Elements presents you with the very foundations of chemical knowledge, explaining concisely the 50 most significant chemical elements. This book uses helpful glossaries and tables to fast track your knowledge of the other 68 elements and the relationships between all of them.

Leseprobe

30-SECOND

ELEMENTS

The 50 most significant elements, each explained in half a minute

Editor

Eric Scerri

Contributors

Hugh Aldersey-Williams

Philip Ball

Brian Clegg

John Emsley

Mark Leach

Jeffrey Moran

Eric Scerri

Andrea Sella

Philip Stewart

First published in the UK in 2013 by

Icon Books

Omnibus Business Centre

39–41 North Road

London N7 9DP

email: [email protected]

www.iconbooks.net

© 2013 by Ivy Press Limited

The editor and contributors have asserted their moral rights.

No part of this book may be reproduced in any form, or by any means, without prior permission in writing from the publisher.

This book was conceived,

designed and produced by

Ivy Press

210 High Street, Lewes,

East Sussex BN7 2NS, UK

www.ivypress.co.uk

Creative Director Peter Bridgewater

Publisher Jason Hook

Editorial Director Caroline Earle

Art Director Michael Whitehead

Project Editor Jamie Pumfrey

Designer Ginny Zeal

Illustrator Ivan Hissey

Glossaries Text Charles Phillips

Science Editor Sara Hulse

ISBN: 978-1-84831-616-4

Colour origination by

Ivy Press Reprographics

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CONTENTS

Introduction

Alkali & Alkaline Earths

GLOSSARY & ELEMENTS

Sodium

Potassium

Francium

Profile: Dmitri Mendeleev

Magnesium

Calcium

Radium

30 Rare Earths

GLOSSARY & ELEMENTS

Promethium

Europium

Gadolinium

Protactinium

Uranium

Profile: Glenn T. Seaborg

Plutonium

Halogens & Noble Gases

GLOSSARY & ELEMENTS

Fluorine

Chlorine

Iodine

Astatine

Profile: Sir William Ramsay

Helium

Neon

Argon

Transition Metals

GLOSSARY & ELEMENTS

Chromium

Iron

Copper

Technetium

Profile: Emilio Segrè

Silver

Hafnium

Rhenium

Gold

Mercury

Copernicium

Metalloids

GLOSSARY & ELEMENTS

Boron

Silicon

Germanium

Arsenic

Antimony

Tellurium

Profile: Marie Curie

Polonium

Other Metals

GLOSSARY & ELEMENTS

Aluminium

Gallium

Profile: Paul Émile Lecoq de Boisbaudran

Indium

Tin

Thallium

Lead

Non-metals

GLOSSARY & ELEMENTS

Hydrogen

Carbon

Nitrogen

Oxygen

Phosphorus

Sulphur

Profile: Pekka Pyykkö

Flerovium

Ununseptium

APPENDICES

Notes on Contributors

Resources

Index

Acknowledgements

INTRODUCTION

Eric Scerri

Interest in the elements and the periodic table has never been greater. Of course, we were all exposed to the periodic table at some point in school chemistry. Everybody remembers the chart that hung on the wall of the chemistry lab or classroom – parts of which we may even have been forced to learn by heart. The chart classifies all the known elements, those most fundamental components that make up the whole earth – and, indeed, the whole universe as far as we know.

But perhaps we didn’t appreciate at the time that the periodic table is without doubt one of the most important scientific discoveries ever made and is fundamental to our knowledge of chemistry today. The core idea is deceptively simple – arrange the elements in order of increasing weight of their atoms and every so often we arrive at an element that shows chemical and physical similarities with a previous one. This doesn’t just happen occasionally in the periodic table but is true of every single element except the very first few, which, of course, have no earlier counterparts in terms of atomic weight.

Dmitri Mendeleev

Russian chemist Dmitri Mendeleev was the first to propose the periodic table of elements as we know it now, as well as predicting the existence of some undiscovered elements. He is commonly referred to as the father of the peroidic table.

As a result of this behaviour, the linear sequence of elements can be arranged in a two-dimensional grid or ‘table’, much like a calendar that shows the recurring days of the week for certain dates in a given month. In this way, the tremendous variety among the elements is brought together into a coherent and interrelated form. Of course, these days we use atomic number (number of protons) to order the elements. But although this has solved a technical problem called ‘pair reversals’, it does not change the periodic table in any major fashion.

Mendeleev’s table, 1871

Antoine Lavoisier’s 1789 catalogue of elements formed the basis for the modern list, but it was not until Mendeleev’s early arrangement in 1869 and final proposal in 1871 that the periodic table was born.

At the time Russian chemist Dmitri Mendeleev and a number of others discovered the periodic system, there was no underlying explanation, no apparent reason why the elements should hang together in this way. But the very fact that all the elements could be successfully accommodated into such an elegant system seemed to suggest deeper things to come. Mendeleev was able to use the periodic table to predict the existence of elements that had never been found before. Within about 15 years, three of his best-known predictions came to be. The discovery of gallium, scandium, and germanium solidified the notion that the periodic system had latched onto a deep truth about the relationship between the chemical elements.

Around the turn of the 20th century many physicists – including J.J. Thomson, Niels Bohr and Wolfgang Pauli – set about trying to understand what lies behind the periodic system. British physicist Thomson, the discoverer of the electron, was one of the first to suggest that the electrons in an atom are arranged in a specific manner that we now call an electronic configuration. Danish physicist Niels Bohr refined these configurations and provided what remains the gist of the explanation for why elements, in fact, repeat every so often, or to put it another way, why it is that certain elements fall into particular groups or vertical columns in the periodic table. Bohr’s answer was that the elements in any vertical column share the same number of outer electrons, building on the emerging notion that chemical reactions are driven by outer electrons.

Next, Austrian physicist Wolfgang Pauli provided a further refinement to the notion of electronic configurations by suggesting that electrons have a hitherto unknown degree of freedom, which became known as ‘spin’. To put it in a nutshell, attempts to understand the periodic system contributed enormously to the development of quantum theory and these quantum ideas, in turn, provided a theoretical foundation for the periodic system of the elements.

Radioactive research

Pierre and Marie Curie gave their lives in pursuit of discovery, living in poverty to fund their research. Their perilous study of the radioactive elements has since contributed to the understanding of modern nuclear physics.

This book will take you on a short and highly digestible tour of 50 of the best known, as well as most intriguing, elements in the periodic table. They range from soft metals, such as sodium, that can be cut with a knife, to the magnificent liquid metal called mercury, to the poisonous gas chlorine that was the world’s first chemical weapon.

Each episode is delivered in just 30 seconds and is presented by the world’s leading experts on the elements with a proven track record for successfully explaining science to a general audience. You will also learn about the historical figures connected with each of the elements, perhaps as the first to have extracted them – or the first to think they had extracted them because there have been many, many dead ends and failed announcements of the discovery of a good number of the elements.

If condensing an account of each element to 30 seconds were not enough, you will also be provided with a 3-second summary plus a 3-minute version to ponder upon. You will read about the practical applications of the elements, their role in history and how they were first discovered. In some cases, you will read about the disputes that took place before they were eventually discovered or created in particle accelerators. You will learn how each element has its own unique ‘personality’, even though their atoms ultimately all boil down to different numbers of protons, neutrons and electrons. The chemistry of the elements essentially reduces to the physics of fundamental particles and yet something seems to defy complete reduction. Why else would the elements show such marked individuality while at the same time conforming to the basic physical laws imposed at the quantum mechanical level?

One is reminded of the amazing diversity in the animal kingdom, all of which sprang from one primordial creature. Evolution has also happened in chemistry, providing another facet to the story of the elements. In this case, the earliest form is still with us today. It is the element hydrogen, which still accounts for more than 75 per cent of the mass of the universe. All the other elements have come from hydrogen, directly or mostly indirectly by the fusion of lighter elements that themselves have their origin in hydrogen. Some parts of this astrophysical synthesis took place soon after the Big Bang, while other elements continue to be formed at the centre of stars and galaxies. The heavier elements, by which I mean anything heavier than iron (atomic number 26), are formed under extreme conditions in supernova explosions.

As somebody who has spent a lifetime studying the elements and the periodic table, I am both humbled and proud to have been the consulting editor and to have contributed to this entertaining and informative tour de force on man’s new best friends – the elements.

All that glitters …

Carbon, found in its most common form as graphite, may seem unappealing, but as one of its other many allotropes, as diamond, it is a much sought-after element.

The Periodic Table

The Periodic Table is organized by atomic number, electron configuration and recurring chemical properties. The rows of the table are called periods, and the columns are known as the groups. First proposed in 1869 with just 60 elements, the table has expanded to accommodate the 118 elements we now know of.

ALKALI & ALKALINE EARTHS

ALKALI & ALKALINE EARTHS

GLOSSARY & ELEMENTS

atom Unit of matter. In an atom, the central nucleus contains positively charged protons and electrically neutral neutrons and is surrounded by negatively charged electrons; in a neutral atom, the number of protons matches the number of electrons.

atomic number The number of protons in an atom’s nucleus.

electron shells The electrons surrounding the atomic nucleus are arranged in energy levels – shells or orbitals. The number of electrons in the outer shell or shells defines an atom’s chemical properties.

emission spectrum The spectrum of light frequencies emitted by an element when it is heated. Scientists use the emission spectrum to identify the elements combined in a sample; for example, in an alloy used by the steel industry. Astronomers use the spectrum to identify elements present in distant stars and galaxies.

half-life The time taken for half the nuclei in a radioisotope (an unstable isotope) to undergo radioactive decay. The half-life is a measure of how stable a radioisotope is.

hydrous Containing water. A hydrous chemical compound is a ‘hydrate’. The opposite, ‘anhydrous’, describes a compound (‘anhydrate’) that does not contain water.

ions Electrically charged particles that form when atoms gain or lose electrons.

isotopes Variants of a chemical element with differing numbers of neutrons in the atomic nucleus. All isotopes of an element have the same number of protons in the nucleus. Isotopes can be natural (naturally occurring) or artificial (man-made). Natural isotopes are either stable or unstable. An unstable isotope is said to be radioactive or a radioisotope; the nucleus splits and ‘decays’, releasing radiation. All artificial isotopes are radioactive.

magic numbers Certain numbers of protons or neutrons in the nucleus make an atom particularly stable, and these are called ‘magic numbers’. These are 2, 8, 20, 28, 50, 82 and possibly 114 or 126 and 184. Where there is a magic number of both protons and neutrons, the nucleus is said to be ‘doubly magic’.

mass number The total number of protons and neutrons in the nucleus of an atom. Protons and neutrons are together called nucleons and the mass number is sometimes called the nucleon number.

molecule Group of two or more atoms held together by covalent bonds (bonds involving the sharing between atoms of pairs of electrons).

reaction Interaction between two or more molecules resulting in chemical change, typically caused by the movement of electrons between atoms that leads to the breaking or forming of chemical bonds.

reactivity A measure of the tendency of an element or other chemical substance to undergo a chemical reaction. A substance is more reactive if it more readily or quickly tends to react with other substances.

ALKALI AND ALKALINE EARTHS

These elements are in groups 1 and 2 of the periodic table. The alkali metals in group 1 are soft metals, silver in colour, that can be cut with a knife. They all have a single electron in their outer shell and are highly reactive. The alkaline earth metals in group 2 are also silver in colour. They have 2 electrons in their outer shell and, as a result, are less reactive than the alkali metals of group 1. They have higher melting and boiling points than the alkali metals.

Alkali Metals

Symbol

Atomic Number

Lithium

Li

3

Sodium

Na

11

Potassium

K

19

Rubidium

Rb

37

Cesium

Cs

55

Francium

Fr

87

Alkaline Earth Metals

Symbol

Atomic Number

Beryllium

Be

4

Magnesium

Mg

12

Calcium

Ca

20

Strontium

Sr

38

Barium

Ba

56

Radium

Ra

88

SODIUM

the 30-second element

This soft, silver-tinted alkali metal is known for its reactivity. Drop a small piece into water and it will fizz energetically as it converts to sodium hydroxide and hydrogen, giving off plenty of heat. Despite being such a dramatic element, sodium is named after its more sedate salt; the word ‘sodium’ comes from soda – not a fizzy drink, but sodium carbonate, an alkaline compound produced from ashes. It is derived from the Arabic suda (‘headache’) because soda was a popular cure for headaches; the chemical symbol is short for natrium, derived from ‘natron’, the old name for washing soda or hydrous sodium carbonate. We come across sodium daily in the yellow glow of street lamps, produced by the strong lines in sodium’s emission spectrum, but we are probably most familiar with sodium in common salt (sodium chloride). Sodium is important for many living things, including humans. It helps regulate our blood pressure and builds up the electrical gradients essential for neurons to fire in our brains. In modern times, our diets tend to contain too much salt, resulting in raised blood pressure and associated health problems.

3-SECOND STATE

Chemical symbol: Na

Atomic number: 11

Named: From ‘soda’ plus the metallic element ending ‘-ium’

3-MINUTE REACTION

The sodium in salt originally came from rocks containing sodium silicate and sodium carbonate, dissolved by rivers and waves crashing over them. There is no natural isolated sodium, but the element occurs widely in minerals, making it the sixth most common element in the earth’s crust, around 2.6 per cent by weight. It is highly reactive due to its atomic structure, with a single electron in its outer shell, which it is more than enthusiastic to give up.

RELATED ELEMENTS

POTASSIUM (K 19)

FRANCIUM (Fr 87)

3-SECOND BIOGRAPHIES

HUMPHRY DAVY

1778–1829

British chemist, first to isolate sodium

JÖNS JACOB BERZELIUS

1779–1848

Swedish chemist who gave sodium the Na symbol

30-SECOND TEXT

Brian Clegg

Sodium regulates blood pressure and gives street lamps their distinctive glow, but it is most familiar to us in the form of sodium chloride (salt).

POTASSIUM

the 30-second element

Potassium is a soft, silvery, alkali metal that was first isolated by British chemist Humphry Davy in 1807. It is too reactive to be used as a metal, but its salts are important. For centuries, potassium nitrate (saltpetre), potassium carbonate (potash), and potassium aluminium sulphate (alum) have been used in gunpowder, soap making and dyeing, respectively. Today potassium sodium tartrate is used in baking powder, while potassium hydrogen sulphite is added to wines to stop rogue yeasts growing, and potassium benzoate is used as a food preservative. All fertilizers contain potassium, and it is mined on a massive scale – around 35 million tons a year – mainly as the mineral sylvite (potassium chloride). Potassium is used in detergents, glass, pharmaceuticals and medical drips. Around 200 tons per year of potassium metal are produced, and most is converted to potassium superoxide. This is used in submarines and space vehicles to regenerate the oxygen in the air when this has become depleted. Superoxide reacts with CO2 to form potassium carbonate and oxygen gas. Potassium is an essential element for living things because, along with sodium, it plays a key role in the operation of the nervous system. Potassium-rich foods include peanuts and bananas.

3-SECOND STATE

Chemical symbol: K

Atomic number: 19

Named: From potash

3-MINUTE REACTION

Potassium is a highly reactive alkali metal of group 1 of the periodic table. It exists only as the positively charged potassium ion K+. Potassium metal dropped into water reacts violently, releasing hydrogen gas, which burns with a lilac flame. Most potassium is the isotope potassium-39, but one atom in 10,000 is potassium-40, which is radioactive – undergoing conversion to argon. This explains why there is 1 per cent of this gas in the earth’s atmosphere.

RELATED ELEMENTS

SODIUM (Na 11)

RUBIDIUM (Rb 37)

CESIUM (Cs 55)

3-SECOND BIOGRAPHIES

HUMPHRY DAVY

1778−1829

British chemist who isolated potassium metal for the first time, by means of electrolysis

JUSTUS VON LIEBIG

1803–73

German chemist who in 1840 proved potassium to be an essential element for plants

30-SECOND TEXT

John Emsley

Potassium, which reacts violently with water, is familiar from its use in detergents and glass, while its superoxide plays a key role in recycling air on board submarines.

FRANCIUM

the 30-second element

The existence of element 87 was predicted by Russian chemist Dmitri Mendeleev in 1871 and it was given the provisional name of ‘eka-cesium’. A number of scientists searched for the element among non-radioactive sources, but did not find it. The eventual discovery was made by Frenchwoman Marguerite Perey, who had worked as a laboratory assistant to Marie Curie in Paris. Perey became skilful in purifying and manipulating radioactive substances and was asked to examine actinium, element 89 in the periodic table. She was the first to observe the radiation produced by actinium itself rather than its radioactive daughter isotopes; her analysis revealed a new element with a half-life of 21 minutes. When she was later asked to name the element in 1946, she chose francium to honour the country of her birth. Francium was the last natural element to be discovered and it has no commercial applications. However, the fact that it has a very large atomic radius and just one outer-shell electron makes it suitable for atomic physics research. A group in the United States has trapped 300,000 atoms of francium and performed several key experiments.

3-SECOND STATE

Symbol: Fr

Atomic number: 87

Named: After France, the country where the element was discovered

3-MINUTE REACTION