Problem 1.9: Using the periodic table explain why sodium

From Chapter 1 Problem Set. Level 3: System Integration.

Question

Using the periodic table, explain why sodium (Group 1) and calcium (Group 2) both form positive ions, but calcium’s ion carries a +2 charge while sodium’s carries +1. Connect your answer to valence electrons.

Answer

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Sodium (Group 1) has one valence electron and donates it to achieve a full outer shell, producing Na⁺. Calcium (Group 2) has two valence electrons and must donate both to reach stability, producing Ca²⁺. Ion charge directly reflects the number of valence electrons an atom must lose.