Naturally occurring tritium is extremely rare on Earth, where trace amounts are formed by the interaction of the atmosphere with cosmic rays. PromethiumÂ is a chemical element withÂ atomic numberÂ 61Â which means there are 61 protons and 61 electrons in the atomic structure. Arsenic occurs in many minerals, usually in combination with sulfur and metals, but also as a pure elemental crystal. There are only certain combinations of neutrons and protons, which formsÂ stable nuclei. TheÂ chemical symbolÂ for Erbium isÂ Er. The difference is a measure of theÂ nuclear binding energyÂ which holds the nucleus together. TheÂ chemical symbolÂ for Argon isÂ Ar. In fact, it's actually possible to have an atom consisting of only a proton (ionized hydrogen). NickelÂ is a chemical element withÂ atomic numberÂ 28Â which means there are 28 protons and 28 electrons in the atomic structure. Consumption of heavy water does not pose a health threat to humans. Silicon is a hard and brittle crystalline solid with a blue-grey metallic lustre, it is a tetravalent metalloid and semiconductor. Bismuth is a brittle metal with a silvery white color when freshly produced, but surface oxidation can give it a pink tinge. For example, actinides with odd neutron number are usually fissile (fissionable with slow neutrons) while actinides with even neutron number are usually not fissile (but are fissionable with fast neutrons). TheÂ chemical symbolÂ for Thulium isÂ Tm. BoronÂ is a chemical element withÂ atomic numberÂ 5Â which means there are 5 protons and 5 electrons in the atomic structure. The name of the gas is formed from two Greek words, meaning water and forming, so this is the element which creates water. TheÂ chemical symbolÂ for Rhenium isÂ Re. The two remaining protons were detected by the “RIKEN telescope”, a device composed of several layers of sensors, positioned behind the target of the RI Beam cyclotron. TheÂ chemical symbolÂ for Technetium isÂ Tc. Europium is one of the least abundant elements in the universe. Hydrogen atoms are so reactive that they combine with almost all elements. To determine the stability of an isotope you can use the ratio neutron/proton (N/Z). HydrogenÂ is a chemical element withÂ atomic numberÂ 1Â which means there are 1 protons and 1 electrons in the atomic structure. It is a colorless, odorless, tasteless, non-toxic, inert, monatomic gas, the first in the noble gas group in the periodic table. Gold is a transition metal and a group 11 element. This equilibrium also known as âsamarium 149 reservoirâ, since all of this promethium must undergo a decay to samarium. Units of measure have been defined for mass and energy on the atomic scale to make measurements more convenient to express. TinÂ is a chemical element withÂ atomic numberÂ 50Â which means there are 50 protons and 50 electrons in the atomic structure. Chlorine is a yellow-green gas at room temperature. TheÂ chemical symbolÂ for Molybdenum isÂ Mo. Naturally occurring potassium is composed of three isotopes, of which 40K is radioactive. NeonÂ is a chemical element withÂ atomic numberÂ 10Â which means there are 10 protons and 10 electrons in the atomic structure. It is plenty in nature with an abundance of 99.98%. Hydrogen generally combines with other atoms in compounds and are usually found in H2( diatomic hydrogen gas). Titanium is resistant to corrosion in sea water, aqua regia, and chlorine. Neptunium metal is silvery and tarnishes when exposed to air. LithiumÂ is a chemical element withÂ atomic numberÂ 3Â which means there are 3 protons and 3 electrons in the atomic structure. TheÂ chemical symbolÂ for Francium isÂ Fr. These have similar chemical properties, but palladium has the lowest melting point and is the least dense of them. MolybdenumÂ is a chemical element withÂ atomic numberÂ 42Â which means there are 42 protons and 42 electrons in the atomic structure. Properties of atomic nuclei (atomic mass, nuclear cross-sections) are determined by the number of protons andÂ number of neutronsÂ (neutron number). Rhodium is a rare, silvery-white, hard, corrosion resistant and chemically inert transition metal. Therefore, we cannot determine the neutron number of uranium, for example. Atomic Mass Number â Does it conserve in a nuclear reaction? Deuterium occurs in trace amounts naturally as deuterium gas, written 2H2 or D2, but is most commonly found in the universe bonded with a protium 1H atom, forming a gas called hydrogen deuteride (HD or 1H2H). Europium is a moderately hard, silvery metal which readily oxidizes in air and water. OxygenÂ is a chemical element withÂ atomic numberÂ 8Â which means there are 8 protons and 8 electrons in the atomic structure. In nuclear industry boron is commonly used as a neutron absorber due to the high neutron cross-section of isotope 10B. TheÂ chemical symbolÂ for Promethium isÂ Pm. Natural boron consists primarily of two stable isotopes, 11B (80.1%) and 10B (19.9%). Titanium is a lustrous transition metal with a silver color, low density, and high strength. On the other hand, nuclei with an odd number of protons and neutrons are mostly unstable. Radon is a radioactive, colorless, odorless, tasteless noble gas. TheÂ chemical symbolÂ for Holmium isÂ Ho. Titanium condenser tubes are usually the best technical choice, however titanium is very expensive material. It is obtained chiefly from the mineral cassiterite, which contains tin dioxide. For other isotopes, the isotopic mass usually differs and is usually within 0.1 u of the mass number. Polonium is a rare and highly radioactive metal with no stable isotopes, polonium is chemically similar to selenium and tellurium, though its metallic character resembles that of its horizontal neighbors in the periodic table: thallium, lead, and bismuth. TheÂ chemical symbolÂ for Rhodium isÂ Rh. TheÂ chemical symbolÂ for Gallium isÂ Ga. Gallium has similarities to the other metals of the group, aluminium, indium, and thallium. It has been synthesized in the laboratory by bombarding tritium with fast-moving deuterium nuclei. RadiumÂ is a chemical element withÂ atomic numberÂ 88Â which means there are 88 protons and 88 electrons in the atomic structure. There are two reasons for the difference between mass number and isotopic mass, known as theÂ mass defect: Note that, it was found theÂ rest mass of an atomic nucleusÂ is measurably smaller thanÂ the sum of the rest masses of its constituentÂ protons,Â neutronsÂ and electrons. Only about 5Ã10â8% of all matter in the universe is europium. RubidiumÂ is a chemical element withÂ atomic numberÂ 37Â which means there are 37 protons and 37 electrons in the atomic structure. It is the eponym of the lanthanide series, a group of 15 similar elements between lanthanum and lutetium in the periodic table, of which lanthanum is the first and the prototype. Actinium gave the name to the actinide series, a group of 15 similar elements between actinium and lawrencium in the periodic table. CC BY-SA 3.0. http://en.wikipedia.org/wiki/Hydrogen_isotopes ArsenicÂ is a chemical element withÂ atomic numberÂ 33Â which means there are 33 protons and 33 electrons in the atomic structure. If there are too many or too few neutrons for a given number of protons, the resulting nucleus is not stable and it undergoesÂ radioactive decay.Â Unstable isotopesÂ decay through various radioactive decay pathways, most commonlyÂ alpha decay,Â beta decay,Â gamma decayÂ orÂ electron capture.