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QuestionChemistry

Helium (He) has an atomic number of 2. Why is it chemically stable?
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Step 1:
I'll solve this problem step by step, explaining the chemical stability of helium:

Step 2:
: Understand Atomic Structure

Helium is the second element in the periodic table with an atomic number of 2, which means it has 2 protons in its nucleus and 2 electrons in its electron shells.

Step 3:
: Electron Configuration

The electron configuration of helium is $$1s^{2}$$, which means:
- It has a completely filled first electron shell (1s orbital) - The 1s orbital contains exactly 2 electrons

Step 4:
: Noble Gas Electronic Stability

Helium is a noble gas, and its chemical stability stems from its complete electron shell configuration. This means: - It has a full valence shell - The 2 electrons completely fill the 1s orbital - There are no unpaired electrons seeking to form chemical bonds

Step 5:
: Octet Rule and Electron Stability

While the octet rule typically applies to elements with 8 valence electrons, helium achieves stability with just 2 electrons because: - Its first (and only) electron shell is completely filled - This configuration represents the lowest energy state for the atom

Step 6:
: Lack of Reactivity

Due to its complete electron shell, helium: - Has no tendency to gain or lose electrons - Does not form chemical bonds easily - Remains chemically inert under most conditions

Final Answer

Helium is chemically stable because its 1s^{2} electron configuration represents a completely filled electron shell, making it energetically unfavorable for the atom to participate in chemical reactions.