MCQ Detailed View

Atoms are made up of three basic particles: protons, neutrons, and electrons. Electrons revolve around the nucleus of an atom in fixed energy levels called shells or orbits. Each shell can hold a specific maximum number of electrons, determined by the formula: 2n², where n represents the shell number (also known as the principal quantum number).

The first shell of an atom is called the K-shell, where n = 1.
Using the formula:
2n² = 2(1)² = 2 electrons.

This means the maximum number of electrons that can occupy the first shell of any atom is 2. No atom can have more than two electrons in its first shell because the quantum mechanical structure of atoms limits the number of electrons allowed in each energy level.

For example:

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  Hydrogen (H) has 1 electron in the first shell.

  
  


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  Helium (He) has 2 electrons in the first shell, completing the shell and making helium chemically stable.

  
  


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  The next element, Lithium (Li), has 3 electrons; two fill the first shell, and the third moves to the second shell (L-shell).

  
  

The second shell (n=2) can hold 8 electrons, the third shell (n=3) can hold 18 electrons, and so on, following the same 2n² rule.

This principle is a key part of atomic structure in Chemistry and is essential for understanding how electrons are arranged in an atom, which directly influences an element’s chemical properties, bonding behavior, and placement in the periodic table.

Thus, the correct answer is 2 electrons, which is the maximum capacity of the first electron shell (K-shell).