Identify the number of valence electrons for Ba
. ? 3 ? 54 ? 8 ? 46 ? 56
The Correct Answer and Explanation is:
Barium (Ba) is an alkaline earth metal found in Group 2 of the periodic table. The number of valence electrons corresponds to the electrons in the outermost shell of an atom. Elements in Group 2 possess two valence electrons. Barium follows this pattern, meaning the correct answer is 2 valence electrons.
Examining the electron configuration of barium provides insight into this conclusion. The atomic number of barium is 56, meaning it has 56 electrons in its neutral state. These electrons arrange themselves within different energy levels, following the order determined by quantum mechanics: 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s² 4d¹⁰ 5p⁶ 6s²
The highest energy level in this configuration is the sixth shell, which contains two electrons (6s²). These are the valence electrons responsible for barium’s chemical properties and reactivity. When forming compounds, barium commonly loses these two outer electrons, resulting in the Ba²⁺ ion. This behavior aligns with the general tendency of Group 2 elements to form divalent cations.
The importance of valence electrons extends to chemical bonding and reactivity. Since barium readily loses its two outermost electrons, it typically forms ionic bonds with nonmetals, such as sulfate (SO₄²⁻) and chloride (Cl⁻), creating compounds like barium sulfate (BaSO₄) and barium chloride (BaCl₂). These interactions illustrate how valence electrons determine the stability and reactivity of an element.
Understanding the number of valence electrons in an atom is essential for predicting chemical behavior, explaining bond formation, and classifying elements within periodic trends. The identification of two valence electrons in barium reinforces its placement in Group 2 and clarifies its common oxidation state of +2 in compounds.
