Which of the following atoms is expected to be the most chemically reactive?

• A. Mg (magnesium)
• B. Na (sodium)
• C. Ne (neon)
• D. Al (aluminum)

Answer: (B)

Verified step by step guidance

1. Identify the group and period of each element in the periodic table: Mg (magnesium) is in group 2, period 3; Na (sodium) is in group 1, period 3; Ne (neon) is in group 18 (noble gases), period 2; Al (aluminum) is in group 13, period 3.
2. Recall that chemical reactivity for metals generally increases as you move down a group and decreases as you move across a period from left to right. For metals in the same period, reactivity is often related to how easily they lose electrons to form positive ions.
3. Consider the electron configurations: Na has one electron in its outermost shell (3s¹), Mg has two (3s²), Al has three (3s² 3p¹), and Ne has a full outer shell (2s² 2p⁶). Atoms with a nearly full or full outer shell (like Ne) are typically very unreactive.
4. Since Na has only one electron to lose to achieve a stable noble gas configuration, it tends to lose that electron more readily than Mg or Al, making it more chemically reactive among the metals listed.
5. Therefore, by comparing their positions and electron configurations, Na is expected to be the most chemically reactive atom among the options given.