Platinum is well known today as a precious metal, but its value is a rather recent facet of history.
More difficult to purify than gold and silver, it was more of a curiosity until modern times. Platinum jewelry is popular and valuable today. Indeed, platinum carries a higher price tag than gold, commemorated in the record industry with the birth of "platinum albums" which represent twice the sales of a mere "gold album". Platinum itself is a very soft metal, so that, like gold, it is not well-suited to making jewelry in its pure form. To improve its strength and hardness, it is usually alloyed with other metals (such as palladium) for use in the jewelry industry.
Platinum is used widely in the chemical industry. As a pure metal, it can be used as a crucible - a container well-suited to heating materials at high temperatures without absorbing or contaminating them. Platinum is commonly used in reference electrodes when conducting potentiometric studies as well. More significant, however, is platinum's role as a catalyst. Powdered platinum (or platinum black) is the most common catalytic form of platinum, and is widely used in organic chemistry work (petrochemical and pharmaceutical applications, for example). Probably most frequently it is used in the hydrogenation of chemicals - that is, adding hydrogen atoms to molecules at electron-rich sites (such as double bonds). So effective is platinum at this role that it is extremely important to keep it away from tanks of hydrogen. A small amount of platinum black is all it takes to lower the activation energy for the combustion of hydrogen to occur spontaneously (at room temperature, without even a spark) in the air. Historic laboratory accidents have led to blatant warning labels, to avoid future fireball situations. Such dramatic accidents have even found their way into fiction. Isaac Asimov (the extremely prolific science fiction author) incorporated the use of platinum black and gas cylinders into tales of murder on more than one occasion.
As a metal, platinum conducts electricity, is malleable and ductile (which is why it works well for jewelry, remember), and has a silvery-grey color. Like gold, it is insoluble in just about anything except "aqua regia", a strong mixture of hydrochloric and nitric acids. (Lesser metals will dissolve in either one acid alone.)
Platinum (Pt) is atomic number 78 on the periodic table, with 78 protons and electrons per atom. There are six known isotopes Pt-190 (112 neutrons, at 0.014% abundance), Pt-192 (114 neutrons, 0.783%), Pt-194 (116 neutrons, 32.968%), Pt-195 (117 neutrons, 33.832%), Pt-196 (118 neutrons, 25.242%), and Pt-198 (120 neutrons, 7.164%).
It has an average atomic mass of 195.08 amu.*
Platinum's melting point is a toasty 1768.4 degrees Celsius, and it boils eventually - at a mere 3825 degrees Celsius.
Even heavier than gold, platinum's density is 21.5 g/cc. (Gold is only 19.3 g/cc.)
The electron configuration for platinum (in shorthand) is [Xe] 6s2, 4f14, 5d8.
Its two most common oxidation states are +2 and +4, as seen with platinum chloride (PtCl2) and platinum oxide (PtO2) as respective examples.
Platinum is not generally a magnetic metal, but nano-research (2007) has shown that small clusters of platinum atoms do exhibit magnetic properties.*
*All numerical data obtained from the 82nd edition of the CRC handbook of Chemistry and Physics.