The term refers to the heaviest elements, starting with actinium and continuing to the end of the periodic table. (cdc.gov)
Background radioactivity - radioactive elements in the natural environment including those in the crust of the earth (like radioactive potassium, uranium, and thorium isotopes) and those produced by cosmic rays. (cdc.gov)
Hydrogen was chosen as the unit of comparison because it was the lightest substance known, and the weights of the other elements would be very close to whole numbers. (encyclopedia.com)
The weight of oxygen could then be calculated because of earlier work by Alexander von Humboldt (1769 - 1859) and Joseph-Louis Gay-Lussac (1778 - 1850), who found that water consisted of only two elements, hydrogen and oxygen, and that there were eight parts of oxygen for every one part of hydrogen. (encyclopedia.com)
Uranium2
Background radioactivity - radioactive elements in the natural environment including those in the crust of the earth (like radioactive potassium, uranium, and thorium isotopes) and those produced by cosmic rays. (cdc.gov)
We find atoms up to about element 92 (uranium) in nature, though trace amounts of some heavier elements like Plutonium-244 have been found. (extremetech.com)
Nucleus5
Alpha particle ( ionizing radiation ) - two neutrons and two protons bound as a single particle (a helium nucleus) that is emitted from the nucleus of certain radioactive isotopes in the process of disintegration. (cdc.gov)
Beta particle ( ionizing radiation ) - a charged particle emitted from the nucleus of certain unstable atomic nuclei (radioactive isotopes), having the charge and mass of an electron. (cdc.gov)
Wo now know that the simplest hydrogen atom is composed of two parts: a) An inner part called the nucleus b) An outer part called the electron shell In later sections, we shall give more details about the nucleus and about the electrons which surround the nucleus. (nih.gov)
We conceive of the hydrogen atom as consisting of a central tiny core or nucleus about which circles a single electron. (nih.gov)
This core or nucleus of the simplest hydrogen atom is called the proton, a proton is simply a hydrogen nucleus and is formed by stripping off an electron from the hydrogen atom. (nih.gov)
Carries1
While a 117-proton atom will be "element 117" regardless of the number of neutrons it carries, only certain isotopes will be amenable to study or application. (extremetech.com)
Electrons1
The number of neutrons in an atom defines which isotope it is, and the number of electrons determines its strength as an ion, but it's the number of protons that distinguishes one element from another. (extremetech.com)
Atom2
A one-proton atom is always hydrogen, a two-proton atom is always helium, and so on. (extremetech.com)
It should bo emphasized that the proton occupies negligible volume inside the hydrogen atom even though it constitutes almost the entire weight of the atom. (nih.gov)