Lithium, sodium, and potassium are grouped together in the periodic table’s first column; what is most likely true about these elements?

• A. They have similar chemical properties
• B. They have completely different properties
• C. They are noble gases
• D. They are nonmetals

Answer: (A)

Elements in the same column share similar chemical behavior because they have the same number of valence electrons in their outer shell, which drives how they bond and react. Lithium, sodium, and potassium each have one valence electron, so they tend to form +1 ions and react in similar ways. They are soft metals with low densities and low melting points, and they react vigorously with water, forming hydrogen gas and metal hydroxides. As you move down this group, the atoms get larger and reactivity increases, but the overarching pattern—similar chemistry among them—stays the same. They are metals, not nonmetals and not noble gases, specifically alkali metals in the first column.