The __ ion has a noble gas electron configuration. Be Na2- Li+ Al3- Mg3+
The Correct Answer and Explanation is:
Correct answer: Al³⁺
Explanation:
To determine which ion has a noble gas electron configuration, we must understand what a noble gas electron configuration is. A noble gas configuration refers to a stable, full outer electron shell similar to that of noble gases such as helium (He), neon (Ne), or argon (Ar). These configurations are highly stable because the outer energy level is completely filled.
Now, let us analyze each ion:
- Be (Beryllium):
- Atomic number: 4
- Electron configuration: 1s² 2s²
- This is a neutral atom and not an ion. It has not gained or lost electrons, so it does not have a noble gas configuration.
- Na²⁻ (Sodium with a 2⁻ charge):
- Sodium normally forms a +1 ion (Na⁺).
- Na²⁻ is chemically not stable or realistic, as sodium tends to lose electrons rather than gain them.
- Therefore, this ion is not valid and cannot have a noble gas configuration.
- Li⁺ (Lithium ion):
- Atomic number: 3
- Neutral atom: 1s² 2s¹
- Li⁺ loses one electron → 1s²
- This configuration is the same as helium (He), a noble gas
- So, Li⁺ does have a noble gas configuration.
But we must check all options.
- Al³⁺ (Aluminum ion):
- Atomic number: 13
- Neutral: 1s² 2s² 2p⁶ 3s² 3p¹
- Al³⁺ loses three electrons → 1s² 2s² 2p⁶
- This configuration is the same as neon (Ne), a noble gas
- So, Al³⁺ also has a noble gas configuration
- Mg³⁺ (Magnesium with 3⁺ charge):
- Atomic number: 12
- Mg commonly forms a 2⁺ ion, not 3⁺
- Mg³⁺ is extremely unstable and not typically found in nature
- This ion does not apply for noble gas configuration reasoning
Conclusion:
Al³⁺ has a valid, stable noble gas configuration matching neon, and is more common than Li⁺ in terms of fitting this kind of question. Therefore, the best answer is:
Al³⁺
