Thulium is an easily workable metal with a bright silvery-gray luster. It is fairly soft and slowly tarnishes in air. Despite its high price and rarity, thulium is used as the radiation source in portable X-ray devices. Thulium is the thirteenth and third-last element in the lanthanide series.
Protons and Neutrons in Thulium
Thulium is a chemical element with atomic number 69 which means there are 69 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 Thulium are 169.
Main Isotopes of Thulium
Thulium occurs only in one natural isotope – 169Tm.
Thulium-169 is composed of 69 protons, 100 neutrons, and 69 electrons.
Typical Unstable Isotopes
|167Tm||9.25 d||electron capture||167Er|
|168Tm||93.1 d||electron capture||168Er|
|170Tm||128.6 d||beta decay||170Yb|
|171Tm||1.92 y||beta decay||171Yb|
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 Thulium is 69. 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 Thulium is [Xe] 4f13 6s2.
Possible oxidation states are +3.
|Number of protons||69|
|Number of neutrons (typical isotopes)||169|
|Number of electrons||69|
|Electron configuration||[Xe] 4f13 6s2|
Properties of other elements