The correct option is **C: it achieves electronic configuration of argon**. ### Detailed Explanation: 1. **Understanding Potassium and Its Ion Formation**: - Potassium (K) is an alkali metal with an atomic number of 19. This means it has 19 protons and, in its neutral state, also 19 electrons. - The electronic configuration of potassium is \(1s^2 2s^2 2p^6 3s^1\). This shows that potassium has one electron in its outermost shell (the 3s subshell). 2. **Ion Formation**: - When potassium forms an ion, it tends to lose its single outer electron to achieve a more stable electronic configuration. This process is driven by the desire to attain a full outer shell, which is characteristic of noble gases. - By losing one electron, potassium becomes a potassium ion (K⁺), which has 18 electrons (19 original electrons - 1 lost electron). 3. **Achieving Argon’s Configuration**: - The noble gas argon (Ar) has an atomic number of 18 and an electronic configuration of \(1s^2 2s^2 2p^6 3s^2 3p^6\). When potassium loses one electron, it achieves the same electron configuration as argon, which is stable due to having a full outer shell. - Therefore, the statement that potassium achieves the electronic configuration of argon when it forms its ion is true. ### Why the Other Options Are Incorrect: - **Option A: it gains one electron and becomes neutral**: - This statement is incorrect because potassium does not gain an electron; it loses one. Gaining an electron would lead to the formation of a negatively charged ion (anion), which is not the case for potassium. - **Option B: its atomic number decreases**: - This statement is also incorrect. The atomic number of an element is determined by the number of protons in its nucleus. When potassium loses an electron to form K⁺, it does not change the number of protons (still 19). Therefore, the atomic number remains the same. - **Option D: it loses one proton**: - This statement is incorrect as well. The loss of a proton would change the identity of the element itself. Potassium remains potassium regardless of whether it is in its neutral state or as an ion. The number of protons (19) does not change when it forms an ion. ### Summary of Key Points: - Potassium (K) loses one electron to form K⁺, achieving a stable electronic configuration. - The electronic configuration of K⁺ is the same as that of argon (Ar), which has a full outer shell. - The atomic number of potassium remains unchanged at 19 during ion formation. - Understanding the behavior of alkali metals in forming ions is crucial for grasping concepts in chemistry related to reactivity and stability. This thorough understanding of potassium's ion formation and its electronic configuration will help you in your studies and in answering similar questions in the future.