Astatine is the rarest naturally occurring element on the Earth’s crust. It occurs on Earth as the decay product of various heavier elements. The bulk properties of astatine are not known with any certainty.
Protons and Neutrons in Astatine
Astatine is a chemical element with atomic number 85 which means there are 85 protons in its nucleus. Total number of protons in the nucleus is called the atomic number of the atom and is given the symbol Z. The total electrical charge of the nucleus is therefore +Ze, where e (elementary charge) equals to 1,602 x 10-19 coulombs.
The total number of neutrons in the nucleus of an atom is called the neutron number of the atom and is given the symbol N. Neutron number plus atomic number equals atomic mass number: N+Z=A. The difference between the neutron number and the atomic number is known as the neutron excess: D = N – Z = A – 2Z.
For stable elements, there is usually a variety of stable isotopes. Isotopes are nuclides that have the same atomic number and are therefore the same element, but differ in the number of neutrons. Mass numbers of typical isotopes of Astatine are 210.
Main Isotopes of Astatine
Astatine does not occur in natural form.
Typical Unstable Isotopes
|209At||5.41 h||beta plus decay or alpha decay||209Po or 205Bi|
|210At||8.1 h||beta plus decay or alpha decay||210Po or 206Bi|
|211At||7.21 h||electron capture or alpha decay||211Po or 207Bi|
Electrons and Electron Configuration
The number of electrons in an electrically-neutral atom is the same as the number of protons in the nucleus. Therefore, the number of electrons in neutral atom of Astatine is 85. Each electron is influenced by the electric fields produced by the positive nuclear charge and the other (Z – 1) negative electrons in the atom.
Since the number of electrons and their arrangement are responsible for the chemical behavior of atoms, the atomic number identifies the various chemical elements. The configuration of these electrons follows from the principles of quantum mechanics. The number of electrons in each element’s electron shells, particularly the outermost valence shell, is the primary factor in determining its chemical bonding behavior. In the periodic table, the elements are listed in order of increasing atomic number Z.
Electron configuration of Astatine is [Hg] 6p5.
Possible oxidation states are .
|Number of protons||85|
|Number of neutrons (typical isotopes)||210|
|Number of electrons||85|
|Electron configuration||[Hg] 6p5|
Properties of other elements