Hafnium is a lustrous, silvery gray, tetravalent transition metal, hafnium chemically resembles zirconium and is found in many zirconium minerals. Hafnium’s large neutron capture cross-section makes it a good material for neutron absorption in control rods in nuclear power plants, but at the same time requires that it be removed from the neutron-transparent corrosion-resistant zirconium alloys used in nuclear reactors.
Protons and Neutrons in Hafnium
Hafnium is a chemical element with atomic number 72 which means there are 72 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 Hafnium are 176-178, 179, 180.
Main Isotopes of Hafnium
Hafnium occurs in 6 natural isotopes: 174Hf, 176Hf, 177Hf, 178Hf, 179Hf and 180Hf. 174Hf is very slightly radioactive, decaying by alpha decay with a half-life of 2×1015 years. 180Hf is the most common isotope, having a natural abundance of approximately 35%.
Hafnium-174 is composed of 72 protons,102 neutrons, and 72 electrons.
Hafnium-176 is composed of 72 protons,104 neutrons, and 72 electrons.
Hafnium-177 is composed of 72 protons,105 neutrons, and 72 electrons.
Hafnium-178 is composed of 72 protons,106 neutrons, and 72 electrons.
Hafnium-179 is composed of 72 protons,107 neutrons, and 72 electrons.
Hafnium-180 is composed of 72 protons,108 neutrons, and 72 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 Hafnium is 72. 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 Hafnium is [Xe] 4f14 5d2 6s2.
Possible oxidation states are +4.
Most Common Compound of Hafnium
While hafnium nitride is the most refractory of all the metal nitrides, hafnium carbide is the most refractory of all the binary materials. With a melting point of about 3900 °C it is one of the most refractory binary compounds known. Because of the technical complexity and high cost of the synthesis, HfC has a very limited use, despite its favorable properties such as high hardness (>9 Mohs) and melting point.
|Number of protons||72|
|Number of neutrons (typical isotopes)||176-178, 179, 180|
|Number of electrons||72|
|Electron configuration||[Xe] 4f14 5d2 6s2|
Properties of other elements