The atmosphere is comprised of gases which are considered to be permanent (gases which remain essentially constant by percent) and gases considered to be variable (gases which have changing concentrations over a finite period of time).he atmosphere is comprised of gases which are considered to be permanent (gases which remain essentially constant by percent) and gases considered to be variable (gases which have changing concentrations over a finite period of time).
, also known as heavy hydrogen) is one of two stable isotopes of hydrogen. The nucleus of deuterium, called a deuteron, contains one proton and one neutron, whereas the far more common hydrogen isotope, protium, has no neutron in the nucleus. Deuterium has a natural abundance in Earth's oceans of about one atom in 7003642000000000000â 6420 of hydrogen.
In the periodic table, americium is located to the right of plutonium, to the left of curium, and below the lanthanide europium, with which it shares many similarities in physical and chemical properties.mericium was first produced in 1944 by the group of Glenn T. Seaborg at the University of California, Berkeley. Although it is the third element in the transuranic series, it was discovered fourth, after the heavier curium.