Final answer:
Element X is most likely an alkali metal from Group 1 of the periodic table, which includes elements that have one valence electron and react violently with water.
Step-by-step explanation:
Element X, described as a metal with one valence electron and that reacts violently with water, most likely belongs to Group 1 of the periodic table. These elements are known as the alkali metals, which include lithium, sodium, potassium, rubidium, cesium, and francium. They are characterized by having a single electron in their outer shell, which is in a s orbital. Alkali metals are exceptionally reactive, especially with water, producing metal oxides and hydrogen gas. They are softer than most metals and can become liquid at temperatures just above room temperature.
Given these properties, it is clear that Element X exhibits traits consistent with the alkali metals, as they react rapidly with oxygen to produce metal oxides and are very soft metals. While Group 2, the alkaline earth metals, are also reactive, they have two valence electrons, a higher ionization energy, and react differently than the alkali metals, making them less likely to be Element X based on the description provided.