A team of Russian and American scientists reported yesterday that they had discovered a new — and very heavy — atomic element. Six atoms of the element were created in a lab by smashing together isotopes of calcium and the radioactive element berkelium in a particle accelerator. The discovery seems to indicate that as new elements become heavier, they also become more stable. For the moment, the element is being called ununseptium, from the Latin referring to the element’s atomic number, 117.