Iodine is the heaviest of the stable halogens, it exists as a lustrous, purple-black metallic solid at standard conditions that sublimes readily to form a violet gas. Iodine is the least abundant of the stable halogens, being the sixty-first most abundant element. It is even less abundant than the so-called rare earths. It is the heaviest essential mineral nutrient.
Protons and Neutrons in Iodine
Iodine is a chemical element with atomic number 53 which means there are 53 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 Iodine are 127.
Main Isotopes of Iodine
Iodine occurs in 2 natural isotopes: 127I and 129I. 129I is very slightly radioactive, decaying by beta decay with a half-life of 1.57×107 years and occurs only in traces. 127I is the most common isotope, having a natural abundance of approximately 100%.
Iodine-127 is composed of 53 protons, 74 neutrons, and 53 electrons.
Iodine-129 is composed of 53 protons, 76 neutrons, and 53 electrons.
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 Iodine is 53. 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 Iodine is [Kr] 4d10 5s2 5p5.
Possible oxidation states are +1,5,7/-1.
Most Common Application of Iodine
Common application of iodine is the tincture of iodine, which is an antiseptic. It is usually 2 to 7% elemental iodine, along with potassium iodide or sodium iodide, dissolved in a mixture of ethanol and water. Tincture solutions are characterized by the presence of alcohol.
|Number of protons
|Number of neutrons (typical isotopes)
|Number of electrons
|[Kr] 4d10 5s2 5p5