Helium atoms are chemically unreactive because
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Correct Answer: Option D
Explanation:
The correct answer is D. The outer electron shell is completely filled.
Here's why:
- Helium (He) is chemically unreactive because its outer electron shell is completely filled with two electrons. This makes it stable and unlikely to react with other atoms, as it already has a full outer shell, which is a key characteristic of noble gases (group 18 elements) in the periodic table.
- Helium's electron configuration is 1s², meaning it has two electrons in its only shell, which is the maximum number of electrons that can occupy the first electron shell. This stability is why helium does not readily form compounds or engage in chemical reactions.
The other options are incorrect because:
- A: Helium atoms do have electrons around the nucleus, but the full outer shell is what makes them stable.
- B: While the number of protons equals the number of electrons in a neutral atom, this fact does not directly explain its chemical inertness.
- C: Helium has two protons and two neutrons, but its chemical unreactivity is due to the full outer shell, not the proton-to-neutron ratio.
- E: Helium atoms contain both protons and electrons (and neutrons in most isotopes), not just protons.
The correct answer is D. The outer electron shell is completely filled.
Here's why:
- Helium (He) is chemically unreactive because its outer electron shell is completely filled with two electrons. This makes it stable and unlikely to react with other atoms, as it already has a full outer shell, which is a key characteristic of noble gases (group 18 elements) in the periodic table.
- Helium's electron configuration is 1s², meaning it has two electrons in its only shell, which is the maximum number of electrons that can occupy the first electron shell. This stability is why helium does not readily form compounds or engage in chemical reactions.
The other options are incorrect because:
- A: Helium atoms do have electrons around the nucleus, but the full outer shell is what makes them stable.
- B: While the number of protons equals the number of electrons in a neutral atom, this fact does not directly explain its chemical inertness.
- C: Helium has two protons and two neutrons, but its chemical unreactivity is due to the full outer shell, not the proton-to-neutron ratio.
- E: Helium atoms contain both protons and electrons (and neutrons in most isotopes), not just protons.