Tungsten (W), a dense, silvery-white metal, possesses a total of six valence electrons. These electrons are located in the outermost shell and are primarily responsible for the element’s chemical reactivity and ability to form bonds. As a transition metal, Tungsten’s electron arrangement is more complex than that of main group elements. This count of six valence electrons explains Tungsten’s wide range of chemical behaviors.
Defining Valence Electrons and Tungsten’s Position
Valence electrons reside in the highest energy level of an atom, determining its chemical interaction. For main group elements, the valence electron count is determined by their group number. Tungsten is in Group 6 and Period 6, suggesting six valence electrons. While this correlation holds true, the conventional rule is complicated for transition metals by the presence of partially filled \(d\) and \(f\) subshells.
Transition metals involve electrons from both the outermost \(s\) subshell and the underlying \(d\) subshell in chemical reactions. The energy levels of the outermost \(s\) and inner \(d\) electrons become very similar. This energy overlap allows both sets of electrons to participate in bonding, which is a defining characteristic of these elements.
The Detailed Electron Configuration of Tungsten
The distribution of electrons is described by the electron configuration. For neutral Tungsten (atomic number 74), the ground state configuration is \([\text{Xe}] 4f^{14} 5d^4 6s^2\). The \([\text{Xe}]\) represents the core electrons, and the filled \(4f^{14}\) subshell is generally non-participatory in bonding.
The valence electrons are found in the outermost energy levels: the \(5d\) and \(6s\) subshells. The \(6s\) subshell contains two electrons (\(6s^2\)), and the underlying \(5d\) subshell is partially filled with four electrons (\(5d^4\)).
Since the \(5d\) and \(6s\) subshells are close in energy, all electrons in both subshells are available for forming chemical bonds. Counting these electrons yields the total valence count: four electrons from \(5d\) plus two electrons from \(6s\). This results in a total of six valence electrons, confirming the assignment for this Group 6 element.
Tungsten’s Common Oxidation States and Bonding Behavior
The chemical behavior of Tungsten is a direct consequence of its six valence electrons. An element’s maximum oxidation state generally corresponds to the total number of valence electrons available for bonding. Tungsten’s most common and stable oxidation state is \(+6\), achieved when all six \(5d\) and \(6s\) valence electrons are utilized, such as in tungsten trioxide (\(\text{WO}_3\)).
This high oxidation state capacity makes Tungsten a powerful electron acceptor. The ability of the \(d\) electrons to participate allows Tungsten to exhibit a variety of lower oxidation states. These lower states, including \(+5, +4, +3,\) and \(+2\), occur when only a fraction of the six valence electrons are involved. This variability is characteristic of transition metals and is rooted in the close energy proximity of the \(5d\) and \(6s\) subshells.