If you had to sum up chemistry in one sentence, it might be this: Atoms need to have full shells of electrons to feel satisfied, and different elements steal, shed, or borrow different numbers of electrons to achieve a full shell.

Atoms of Element 118 fill an outer shell with electrons, creating a special type of element called a noble gas. Noble gases are natural turning points on the table, ending one row and pointing to the next.

Atoms consist of a positive nucleus and negative electrons flying around outside it. Electrons closest to the nucleus feel a strong negative-on-positive tug, and the bigger atoms get, the bigger the tug. In really big atoms, electrons whip around at speeds close to the speed of light.

Many different elements can form isomers, but only a few elements on the periodic table, like hafnium, can form isomers that last more than fractions of a second - and might therefore be turned into weapons.

In some sense, what you might have suspected from the first day of high-school chemistry is true: The periodic table is a colossal waste of time. Nine out of every 10 atoms in the universe are hydrogen, the first element and the major constituent of stars. The other 10 percent of all atoms are helium.

Scientists have continued to tinker with different elements and have learned new ways to store and deliver energy.