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Samarium – Periodic Table – Atomic Properties


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.


Element Samarium
Atomic number 62
Atomic mass [amu] 150.36
Atomic mass [pm] 198
Density at STP [g/cm3] 7.353
Number of protons 62
Number of neutrons (typical isotopes) 149, 150, 152, 154
Number of electrons 62
Electron configuration [Xe] 4f6 6s2
Oxidation states +2,3
Electron affinity [kJ/mol] 50
Electronegativity [Pauling scale] 1.17
First ionization energy [eV] 5.6437

Atomic Number – Protons, Electrons and Neutrons in Samarium

Proton Number - Atomic NumberSamarium 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.

Atomic Mass of Samarium

Atomic mass of Samarium is 150.36 u. 

The atomic mass is the mass of an atom. The atomic mass or relative isotopic mass refers to the mass of a single particle, and therefore is tied to a certain specific isotope of an element. The atomic mass is carried by the atomic nucleus, which occupies only about 10-12 of the total volume of the atom or less, but it contains all the positive charge and at least 99.95% of the total mass of the atom. Note that, each element may contain more isotopes, therefore this resulting atomic mass is calculated from naturally-occuring isotopes and their abundance.

Atomic Radius of Samarium

The atomic radius of Samarium atom is 198pm (covalent radius).

Atomic Radius of Chemical Elements

It must be noted, atoms lack a well-defined outer boundary. The atomic radius of a chemical element is a measure of the distance out to which the electron cloud extends from the nucleus. However, this assumes the atom to exhibit a spherical shape, which is only obeyed for atoms in vacuum or free space. Therefore, there are various non-equivalent definitions of atomic radius.

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.

Density of Samarium

Density of Samarium is 7.353g/cm3.

Typical densities of various substances are at atmospheric pressure.

Density is defined as the mass per unit volume. It is an intensive property, which is mathematically defined as mass divided by volume:

ρ = m/V

Atomic Masses of Elements

Periodic Table of Elements - atomic mass

Atomic Radii of Elements

Periodic Table of Elements - atomic radius

Densities of Elements

Periodic Table of Elements - density



Electron Affinity – Samarium

Electron affinity of Samarium is 50 kJ/mol.

In chemistry and atomic physics, the electron affinity of an atom or molecule is defined as:

the change in energy (in kJ/mole) of a neutral atom or molecule (in the gaseous phase) when an electron is added to the atom to form a negative ion.

X + e → X + energy        Affinity = – ∆H

In other words, it can be expressed as the neutral atom’s likelihood of gaining an electron. Note that, ionization energies measure the tendency of a neutral atom to resist the loss of electrons. Electron affinities are more difficult to measure than ionization energies.

Electronegativity of Samarium

Electronegativity of Samarium is 1.17.

Electronegativity, symbol χ, is a chemical property that describes the tendency of an atom to attract electrons towards this atom. For this purposes, a dimensionless quantity the Pauling scale, symbol χ, is the most commonly used.

The electronegativity of Samarium is: χ = 1.17

First Ionization Energy of Samarium

First Ionization Energy of Samarium is 5.6437 eV.

Ionization energy, also called ionization potential, is the energy necessary to remove an electron from the neutral atom.

X + energy → X+ + e

where X is any atom or molecule capable of being ionized, X+ is that atom or molecule with an electron removed (positive ion), and e is the removed electron.

A Samarium atom, for example, requires the following ionization energy to remove the outermost electron.

Sm + IE → Sm+ + e        IE = 5.6437 eV

Electronegativity of Elements

Periodic Table of Elements - electronegativity

Ionization Energy of Elements

Periodic Table of Elements - ionization energy


Source: www.luciteria.com


Properties of other elements

Samarium - Comparison of Atomic Properties

Periodic Table in 8K resolution

Other properties of Samarium