4 Number of elements present 3 minutes after the Big Bang. Because of the extreme temperature, hydrogen, helium, lithium, and beryllium existed only as bare atomic nuclei. About 300,000 years later, things had cooled enough to form atoms.
117 Atomic number (indicating the number of protons) of ununseptium, the newest element on the periodic table. Discovered in the form of six atoms produced in Russia’s U400 cyclotron in April 2010, it is the fifth element added in the past decade. The periodic table’s heavyweight, ununoctium (with 118 protons), was synthesized by physicists at Lawrence Berkeley National Laboratory in 2006.
8x10^24
Half-life, in years, of tellurium-128, the longest among all radioactive isotopes. Beryllium-13 lasts just 2.7×10-21 second. Potassium-40, with a half-life of 1.3 billion years, helps to date geologic samples, while carbon-14, with a 5,730-year half-life, is useful for measuring the age of organic materials such as bone and wood.
130 Million Number of years a typical atom of bromine spends in the ocean, the longest residence time of any element. Atoms of tin, one of the most reactive elements in the ocean, remain there for just five years.
72 Abundance of hydrogen in the universe, as a percentage of its total mass. The runners-up are helium, at 26 percent, and oxygen, at 1 percent. On Earth, oxygen is the most abundant in both the crust (46 percent) and the ocean (86 percent). Elements 91, protactinium, and 85, astatine, are among the rarest on the planet—Earth’s total reserves of the latter are thought to total less than 1 ounce.
$2,500 Price per ounce of rhodium (at press time), the most expensive element on Earth. It is used in jewelry, aircraft spark plugs, and lab crucibles. Other elements that fetch top prices include platinum ($1,544 per ounce), gold ($1,243), and iridium ($750).
