The Properties the Transition Metals are largely dependent on the electronic configuration of the electrons in the outer shell and in the penultimate outer shell. The transition elements readily form alloys with themselves and with other elements (e.g. a copper-tin alloy is used for mirrors, brass is a copper-zinc alloy). Tungsten is used to make tools and filaments in light bulbs. The atomic size is fairly constant since the electrons in the outer most shells have similar environments. The elements in this group can have different oxidation states, which make them useful as catalysts. Compounds of the transition elements can be paramagnetic (i.e. attracted by a magnetic field) or diamagnetic (i.e. not attracted by a magnetic field). Magnetism in the transition elements is caused by the presence of unpaired electrons in the sub-orbital. Un-magnetism is characteristic of compounds where all the electrons are paired in the sub-orbitals. Apart from Copper, the transition metals are all white metals. They vary widely in abundance (e.g. Iron, Fe, and Titanium, Ti, are plentiful, Scandium, Sc, is rare). They have high melting points and high densities. This suggests that the electrons which enter the orbitals are being used to bind the atoms together in the crystal lattice. The transition elements form Complex Ions.
The early chemists were keen to try and find patterns in the elements. A man called John Newlands had a go at arranging the elements in a logical order in 1863. He noticed that every 8th element had similar properties and so he listed some of the known elements in rows of 7. These sets of eight were called Newlands octaves but unfortunately the pattern broke down on the third row with many transition metals like Fe, Cu, and Zn ruining the pattern. It was because he left no gaps that his work was ignored. However he was quite close. In 1869 Dmitri Mendeleyev from Russia, with knowledge of approximately 50 known elements, arranged them into his table of elements with various gaps. Mendeleyev ordered the elements in order of atomic mass (like Newlands did). But mendeleyev found he had to leave gaps in order to keep elements with similar properties in the same vertical groups and he was prepared to leave some very big gaps in the first two rows before the transition metals come in on the third row.
The gaps were very clever because they predicted the properties of so far undiscovered elements. When they were found they fitted the pattern.
As you go down Group 7 the halogens they become bigger atoms because there is one extra full shell of electrons for each row you go down, they become less reactive because there is less inclination to gain the extra electron to fill the outer shell when it’s further out from the nucleus, they become darker in colour, they go from gas to solid e.g. fluorine and chlorine are gases and bromine is a liquid and iodine is a solid. As you progress downwards their melting and boiling points become higher.
All the halogens are non-metals with coloured vapours :fluorine is very reactive, poisonous yellow gas.
Chlorine is a fairly reactive poisonous dense green gas
Bromine is a dense, poisonous, red/brown volatile liquid.
Iodine is a grey crystalline solid or a purple vapour.
Halogens form molecules, which are pairs of atoms. The halogens do both ionic bonding and covalent bonding. They form ions with a 1- charge: F- Cl- Br- I-. They form covalent bonds with themselves and in various molecular compounds.
Halogens react with metals to form salts. They react with most metals including iron and aluminium to form salts (or “metal halides”). More reactive halogens will displace less reactive ones. Chlorine can displace bromine and iodine because of the trend in reactivity. Halogens react with hydrogen. The halogens form covalent compounds with hydrogen. Fluorine and chlorine can explode as they react with hydrogen bromine and iodine only react slowly.
As you go down group 0, the Noble gases, the density increases because the atomic mass increases, and the boiling point increases e.g. helium boils at –260 C and xenon boils at –108 C. All of the Noble gases have full outer shells, that is why they are so inert. Inert means “doesn’t react”. All of the Noble gases are colourless, monatomic gases, most gases are made up of molecules, but these only exist as individual atoms, because they wont form bonds with anything. The Noble gases don’t react with at all. Helium, neon and argon don’t form any kin of chemical bonds with anything. They always exist as separate atoms. They won’t even join up in pairs.
Some uses of Noble gases. Helium is used in airships and balloons, it is ideal as it has a very low density and doesn’t set on fire, neon is used in electrical discharge tubes, when a current is passed through neon it gives out a bright light, argon is used in filament lamps, it provides an inert atmosphere which stops the very hot filament from burning away all three of the previous Noble gases are used in lasers, you can also get krypton lasers.
