To determine the valency of an element using its electron configuration, you need to examine the outermost energy level (also known as the valence shell) and determine the number of electrons it contains. The valency of an element corresponds to the number of electrons it can gain, lose, or share to achieve a stable electron configuration.
Scandium (Sc) has an atomic number of 21, so its electron configuration can be written as: 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹.
In this case, the outermost energy level of scandium is the 4s subshell. The 4s subshell contains 2 electrons. Since the stability goal is typically to achieve a full valence shell (usually 8 electrons for main group elements), scandium can either lose these two electrons to have an empty 4s subshell or it can share them to form compounds.
Based on this analysis, the valency of scandium can be determined to be +2. Scandium can lose its two 4s electrons to form Sc²⁺ ions, achieving the electron configuration of argon (1s² 2s² 2p⁶ 3s² 3p⁶) which has a full valence shell.
It's worth noting that scandium can also exhibit other oxidation states depending on the specific compound or reaction it is involved in. However, the +2 valency is the most common for scandium.