Question

Anything that influences the valence electrons will affect the chemistry of the element. Which one of the following factors does not affect the valence shell?

• A. Valence principal quantum number (n)
• B. Nuclear charge (Z)
• C. Nuclear mass
• D. Number of core electrons

Answer 1

The Correct Option is C

 

1. Valence principal quantum number (n): The principal quantum number, denoted by \(n\), determines the energy level and size of the valence shell. It is directly related to how far the valence electrons are from the nucleus and hence affects their energy and the chemistry of the element. Therefore, \(n\) significantly affects the valence shell.
2. Nuclear charge (Z): This is the positive charge of the nucleus due to protons. An increase in nuclear charge pulls valence electrons closer to the nucleus, reducing atomic radius, and can affect valence electron energy and reactivity. Thus, nuclear charge plays a significant role in influencing the valence shell.
3. Number of core electrons: Core electrons provide shielding or screening effect, reducing the effective nuclear charge felt by the valence electrons. This affects the energy and reactivity of the valence electrons, thereby impacting the valence shell.
4. Nuclear mass: The nuclear mass primarily depends on neutrons, which do not exert an electric force on electrons. While it influences isotopic behavior and stability, it does not directly affect the energy levels or behavior of valence electrons in the shell. Thus, nuclear mass does not affect the valence shell.

Based on the explanations above, the factor that does not affect the valence shell is Nuclear mass.

Thus, the correct answer is Nuclear mass.