The discovery of Gallium made chemists at the time certain that Mendeleev was correct in his development and order of the P.Table. The main reason for this is that Mendeleev’s prediction for the properties Eka-Alluminium was almost identical to the properties of Gallium. Therefore chemists awaited and tried to discover other elements that Mendeleev had predicted.
Gallium is a very odd element because some of its properties suggest it is a metal, whilst others suggest that it is a non metal.
One of the most extraordinary things about gallium is its low melting point of only 29.78°C. This means that is liquid near room temperatures or in hot countries. This is particularly good as it can be used in glass thermometers.
Being quite uncreative, it is also a safe option.
Gallium also has an extremely high boiling point of about (2403°C). This also makes is suitable to be used in high temperature glass thermometers.
Most elements expand when heated and contract when cooled. But just like water, Gallium expands upon freezing. This is because it “is denser as a liquid than as a solid, and hence it will solidify from the top down”
The properties and facts that suggest Gallium is a metal are:
1) It is in the metals section in the periodic table.
2) It behaves similarly to aluminium and other metals when reacting with acids and alkalis.
3) Gallium is blue-grey in colour as a solid and silvery as a liquid. This is also indicating physical properties like metals. (E.g. mercury is a silver liquid)
4+5) Gallium also acts as a semiconductor of heat and electricity. This means that it is more of a metal than a non-metal. Also, “Gallium easily forms alloys with most metals and has been used to create low melting alloys.”
The properties or facts that suggest that gallium is a non metal are:
1+2) Its low melting point and that gallium is denser as a liquid than a solid and hence behaves like water (non-metal).
3) Gallium also bonds covalently with other gallium atoms and even some compounds. This is a feat commonly exhibited by non-metals.
Atomic spectroscopy was one of the methods widely used even in the past, to discover new elements. The UNILAC accelerator is now used for the modern periodic table.
“The Universal Linear Accelerator is based at the Heavy Ion Research Centre (GSI) near . Its use has produced, in the past 20 years, elements to and the creation of element is expected very soon.”
This involves firing heavy ions from an accelerator towards another heavy, stable element (e.g. lead).
If successful, the ions will attract each other, overcoming the nuclear repulsion and hence fuse together; creating a new, heavier element. Most of the times, the new element is radioactive and hence will decay. As the atomic number of the element increases, the longer it takes to fuse the nuclei and the faster the decay of the new element
This has lead to a slow production of elements and will become extremely hard after element 113.
Atomic spectroscopy is the determination of elemental composition by its electromagnetic or mass spectrum. This is divided into mass or optical spectroscopy.
When atoms gain or absorb energy, they become excited and hence progress to different energy levels. If the energy is high enough, the atom will be ionised.
“When these excited atoms lose their energy, they return to their ground state, and energy is often emitted as radiation.”
The energy absorbed and emitted has a specific frequency, which is determined by the quantised gaps in the energy levels.
Spectroscopy is the study of this radiation that atoms emit. This emitted energy is usually in the form of electromagnetic radiation.
The mass spectrometer “distinguishes chemical species in terms of their different isotopic masses.”
Atoms can be deflected by magnetic fields (ionic). The sequence is:
Stage 1: Ionisation: The atom is ionised by knocking one or more electrons off to give a positive ion.
Stage 2: Acceleration: “The ions are accelerated so that they all have the same kinetic energy.”
Stage 3: Deflection: The ions are then deflected by a magnetic field according to their masses. The lighter they are, the more they are deflected. The more the ion is charged, the more it gets deflected.
Stage 4: Detection: “The beam of ions passing through the machine is detected electrically.”
In the past, elements were discovered (as in history) by finding them amongst other ores or compounds.
As time has progressed, elements are now synthesised and not actually discovered. I.e. elements are made from other elements rather than discovering them in their natural state. This is mainly done by “firing metal ions into metal targets and hence fusing the nuclei together to form a new element”. The task became harder by the element and this meant that organisations would compete to discover elements or even “fight over the rights to name elements.”
References and key:
Book: Chemical Ideas ~ Salters Advanced Chemistry.
Article1 and Article2: provided.
Microsoft Encarta Encyclopaedia 2006 REF Article “The Atom”.
Note: all diagrams that have a blue border have either been hand drawn on the computer or labels added by me.
