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Structure
Big Questions
A carbon atom

Will we discover any more elements?

Mendeleev's periodic table may have the same structure as the modern equivalent, but it contained only 88 elements, it finished at element 92, and had 4 gaps. Since then we have discovered many more elements. It is believed that we now know all of the elements that occur naturally on our planet, but it is possible that there are still many undiscovered elements, perhaps elements that are not normally found on Earth. Bombarding atoms with high energy particles in order to literally metamorphose one element into another is also possible. Particle accelerators speed up the particles within an atom until they collide, creating enough energy to produce new elements. Sometimes only minor quantities of these new elements have been made. For instance, scientists who made element 109 produced only one atom, and within milliseconds it had decayed.

Currently, we do not know the atomic weight of elements 110 and 111 since they were only produced once: scientists have not yet managed to make them again. Element 114 was discovered in 1999, but is only existed for a mere 30 seconds! Elements 116 and 118 were discovered in 1999, but again, they were only in existence for less than a millisecond, since they decay very rapidly.

Our ability to discover new elements may be limited to the technology that we currently possess.

For more information about the elements, visit Chemsoc, the Royal Society of Chemistry’s chemical science network (www.chemsoc.org)

Silicon

Can silicon-based life forms exist?

Living things are largely composed of water and all the chemical reactions in our bodies, metabolism, take place in solution in water, so it is an essential component of all living things. Living things also contain carbohydrate, fat, protein, vitamins, nucleic acids and minerals. With the exception of the minerals, these are organic carbon-based substances. Our flesh is mainly protein and this contains carbon, hydrogen, oxygen, nitrogen and a little sulphur. The reactions in our bodies only go fast enough because they are catalysed by enzymes and these too are protein molecules. The energy required for movement, growth, repair and to keep us warm comes from carbohydrates. These chemicals contain carbon, hydrogen and oxygen as does fat. Our DNA is yet another carbon-containing chemical. The one common feature of these chemicals is that they all have a carbon chain to which various other atoms are bonded. All life on Earth is carbon based. Organic chemistry is the study of compounds of carbon including many chemicals not found in living things.

Biologists have noted the proximity of carbon and silicon in the periodic table. Both elements are in Group 4 of the periodic table. NB Modern chemists now refer to these elements as Group 14. Elements in the same Group of the periodic table have very similar properties. In fact our cells have difficulty in distinguishing between calcium and strontium, both in Group 2 of the periodic table. Some scientists have supposed that it might be possible for some kind of life form to develop using silicon instead of carbon as the basis for life. Such organisms might have evolved on other planets in remote solar systems under very different conditions or even in the fiercely hot magma beneath the Earth’s crust.

The possibility of silicon-based life forms is fascinating. But although the chemistry of silicon is similar to that of carbon, there are significant differences. Metabolism, the chemical reactions in living things, can be divided into two kinds of reactions. Anabolic reactions take simple chemicals and build more complex ones from them using an energy source. Chemosysnthesis, photosynthesis, growth and repair are all anabolic processes. The idea of silicon-based life supposes that there is a simple silicon compound and suitable solvent that could be chemically combined into more complex chemicals. Digestion, decay and respiration are all catabolic processes. Complex chemicals are broken into simpler ones releasing energy required for other purposes. The idea of silicon-based life supposes that there are complex silicon chain macromolecules that could serve the functions of carbohydrates, fats, proteins, vitamins and nucleic acids.

Silicon dioxide is a solid. However it is very abundant on Earth: sand! Perhaps on another planet there might be a suitable gaseous or liquid silicon substance. This might be silicon dioxide at much higher temperatures and pressures than here on Earth. It might be silicon nitride, silicon hydride, silicon chloride or some other covalent compound. The first essential requirement for a silicon-based life form is the possibility of converting a simple silicon compound into a more complex and stable one using an energy source, heat, electricity, light, sound? The second essential requirement for silicon-based life is the existence of complex silicon compounds that can serve as energy sources, catalysts for silicon metabolism and control or information substances. The third essential requirement for silicon-based metabolism is the existence of a suitable solvent. This need not be water. There are over 100 different elements and therefore millions of possible combinations of them. The possibility of silicon-based life is an interesting research topic. It is worth noting that a silicon-based microbe would be unable to utilise our cells as an energy source, though a silicon-based alien lifeform could exist.

Click here for more information about silicon.

Testing in situ

How do chemists discover new drugs?

Did you know that there are over 100,000 new molecules being made every year? These molecules are new materials that could save lives in the future.

In order to discover new drugs, and to improve the drugs that are currently available, chemists have to find out which molecules are most effective. To do this, they use combinatorial chemistry. This is a relatively new technology that allows the manufacture of thousands of different molecules, which can be tested at the same time. Only 15 years ago, chemists could only test one molecule at a time, to see if they affected biological activity that could help fight disease. This form of testing was quite long-winded and progressed to using polymer beads in order to test new materials. Nowadays, tests are done on silicon chips – and chemists can test over 100,000 different ratios of reactants per day, and in very tiny amounts. This means that scientists can assess reactions to identify promising molecules. The most promising molecules can. It is even possible to create ‘virtual’ molecules on the computer and test them by modelling their actions in the body, before they are even made. This is how new pharmaceuticals are made: scientists use the traditional scatter-shot technique of creating molecules, but in a smart way.

To find out more about new drugs, go to the British Pharmacology Society.

Electrified plasma gas

Are there more than 3 states of matter?

Whether a substance is liquid, gas or solid should be easy to identify, shouldn't it? You would've thought so, but did you know that there are actually 'in between states', that there are more states than just liquid, gas and solid? A substance can look like a solid but may actually be more liquid than solid!

Take elastic, for example. This is more liquid than solid since it behaves in way that defies the usual definitions of a 'solid'. Liquid crystal is another example of a substance that does not fit into the usual definition of state.

And what is plasma, then? Is it a liquid, or is it a solid? Plasma is actually a fluid made up of electrically charged particles. Some or all of the electrons are stripped off the atoms, leaving positively charged ions and electrons. Its properties are very specific because of this electrical charge, making it behave very differently from other states of matter, hence plasma is often referred to as the 4th state of matter. Plasma is formed when atoms are broken up into parts, as opposed to combining with other atoms to form complex structures as with solids, liquids and gases. This plasma state of matter is of great importance to our future energy source: it plays a key part in nuclear fusion reactions.

For more information about the states of matter, go to Chemtutor.com

Quark

What's the smallest particle that exists?

The first sub-atomic particle to be discovered was the electron, in 1870s by a scientist called J.J. Thomson, with Rutherford discovering the proton in 1919, and in 1932, James Chadwick discovered the neutron. It was thought that protons, neutrons and electrons were the smallest particle in existence. But then, it was discovered that many fundamental particles exist. In 1964, a physicist called Murray Gell-Mann found that there were 200 sub-atomic particles that could be reduced to 'fundamental' particles called quarks: and that there are actually different types of quarks, and they combine in different ways. The first 5 quarks have been named 'up', 'down', 'strange', 'charm', and 'bottom'. A 6th quark, called 'top', was discovered only in 1995!

There is a theory that quarks are the key to the beginning of all things; that a kind of quark-electron soup led to the formation of hydrogen, helium and lithium nuclei.

It is widely thought that quarks are the smallest particle that exists. The future of sub-atomic discovery could remain with our present theory that quarks are the smallest particles that exist, but there are more 'theoretical' particles: for example, Gluons are hypothetical sub-atomic particles that are thought to play a part in the way quarks interact, by channelling the attractive force between each quark particle. It is thought that the 6 quark types are held together by gluons - there are currently thought to be 8 different kinds of gluon. This field of chemistry is called quantum chromodynamics.

To find out more about sub-atomic particles, go to The Science Museum.

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