The element with atomic numbers 43 (Technetium) and 61 (Promethium) are unique because they are the only radioactive elements before the start of the bulk of the radioactive elements. The bulk of the radioactive elements begins at atomic number 84 (Polonium). These are significant as they aren't primordial and are only found due to radioactive decay.
Today all elements up to atomic number 98 (including Cf) are considered as natural chemical elements.
The elements with atomic numbers 43, 61, and 93-109 are all transition metals on the periodic table. They have partially filled d-orbitals and exhibit similar chemical properties related to their ability to form complex ions and exhibit variable oxidation states.
Technetium (Tc) has atomic number 43, which means it has 43 electrons.
Technetium, atomic number 43 Promethium, atomic number 61 Astatine, atomic number 85 Francium, atomic number 87 Neptunium, atomic number 93 Plutonium, atomic number 94 Transuranium elements Americium symbol Am, atomic number 95 Curium symbol Cm, atomic number 96 Berkelium symbol Bk, atomic number 97 Californium symbol Cf, atomic number 98 Einsteinium symbol Es, atomic number 99 Fermium symbol Fm, atomic number 100 Mendelevium symbol Md, atomic number 101 Nobelium symbol No, atomic number 102 Lawrencium symbol Lr, atomic number 103 Transactinide elements Rutherfordium symbol Rf, atomic number 104 Dubnium symbol Db, atomic number 105 Seaborgium symbol Sg, atomic number 106 Bohrium symbol Bh, atomic number 107 Hassium symbol Hs, atomic number 108 Meitnerium symbol Mt, atomic number 109 Darmstadtium symbol Ds, atomic number 110 Roentgenium symbol Rg, atomic number 111
Technetium has 34 isotopes, with no stable isotopes
All elements lighter than Uranium (atomic number: 92) occur naturally except for technetium (43).
92 Today natural elements are considered the elements up to the atomic number 98; but the elements with atomic numbers 43, 61 and 93-98 exist only in extremely traces, as a curiosity in uranium deposits. Of course they can be obtained also by man made nuclear reactions. Consequently man made elements must be considered only the elements with the atomic number over 98: some examples are meitnerium, bohrium, flerovium.
Today all elements up to atomic number 98 (including Cf) are considered as natural chemical elements.
The 26 transuranic elements (elements with atomic numbers higher than 92) are man-made. Some lists also count technetium (element 43) as man-made as well. --------------- Now (January 2013) 97 chemical elements are considered as natural and 21 as man made.
The elements with atomic numbers 43, 61, and 93-109 are all transition metals on the periodic table. They have partially filled d-orbitals and exhibit similar chemical properties related to their ability to form complex ions and exhibit variable oxidation states.
Of elements that have no stable isotopes, technetium has the lowest atomic number, which is 43.
The atomic number of technetium (Tc) is 43.The atomic weight of Tc is 98 grams per mole.See the Web Links to the left of this answer for a periodic table with more information about this element!
from 88-95
The atomic mass of Ca-43 is approximately 43 amu (atomic mass units). This value represents the total mass of an atom of calcium-43, taking into account the protons, neutrons, and electrons that make up the atom.
A chemical element is a type of atom distinguished by its atomic number; which is the number of protons in its nucleus. The term is also used to refer to a pure chemical substance composed of atoms with the same number of protons. Common examples of elements are iron, copper, silver, gold, hydrogen, carbon, nitrogen, and oxygen. In total, 117 elements have been observed as of 2008, of which 94 occur naturally on Earth. 80 elements have stable isotopes, namely all elements with atomic numbers 1 to 82, except elements 43 and 61 (technetium and promethium). Elements with atomic numbers 83 or higher (bismuth and above) are inherently unstable, and undergo radioactive decay. The elements from atomic number 83 to 94 have no stable nuclei, but are nevertheless found in nature, either surviving as remnants of the primordial stellar nucleosynthesis which produced the elements in the solar system, or else produced as short-lived daughter-isotopes through the natural decay of uranium and thorium. All chemical matter consists of these elements. New elements of higher atomic number are discovered from time to time, as products of artificial nuclear reactions.
43 = XLIII
1 and 43