Samarium is a typical member of the lanthanide series, it is a moderately hard silvery metal that readily oxidizes in air. The name samarium is after the mineral samarskite from which it was isolated. Although classified as a rare earth element, samarium is the 40th most abundant element in the Earth’s crust and is more common than such metals as tin. In nuclear industry, especially natural and artificial samarium 149 has an important impact on the operation of a nuclear reactor. Samarium 149 has a very large neutron capture cross-section (about 42,000 barns). Since natural samarium contains about 14% of 149Sm, it can be used as an absorbing material in control rods.
Protons and Neutrons in Samarium
Samarium is a chemical element with atomic number 62 which means there are 62 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 Samarium are 149, 150, 152, 154.
Main Isotopes of Samarium
Samarium occurs in 7 natural isotopes: 144Sm, 147Sm, 148Sm, 149Sm, 150Sm, 152Sm and 154Sm. 152Sm is the most common isotope, having a natural abundance of approximately 26%. Of these, 147Sm and 148Sm are very slightly radioactive, decaying both by alpha decay with a half-life of 1.06×1011 years and 7×1015 years.
Samarium-144 is composed of 62 protons, 82 neutrons, and 62 electrons.
Samarium-147 is composed of 62 protons, 85 neutrons, and 62 electrons.
Samarium-148 is composed of 62 protons, 86 neutrons, and 62 electrons.
Samarium-149 is composed of 62 protons, 87 neutrons, and 62 electrons.
Samarium-150 is composed of 62 protons, 88 neutrons, and 62 electrons.
Samarium-152 is composed of 62 protons, 90 neutrons, and 62 electrons.
Samarium-154 is composed of 62 protons, 92 neutrons, and 62 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 Samarium is 62. 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 Samarium is [Xe] 4f6 6s2.
Possible oxidation states are +2,3.
Most Common Application of Samarium
Samarium is mainly used in preparing samarium-cobalt alloy magnets for electric guitars, small motors and headphones. These samarium–cobalt magnet alloys (generally written as SmCo5, or SmCo Series 1:5) have one atom of rare-earth samarium per five atoms of cobalt. By weight this magnet alloy will typically contain 36% samarium with the balance cobalt. Samarium-cobalt magnets are much more powerful than iron magnets. They remain magnetic at high temperatures and so are used in microwave applications.
|Number of protons||62|
|Number of neutrons (typical isotopes)||149, 150, 152, 154|
|Number of electrons||62|
|Electron configuration||[Xe] 4f6 6s2|
Properties of other elements