Question

helium (he) and neon (ne) are elements in group 8a of the periodic table. how do the electron dot diagrams of these elements compare?
the electron dot diagram of helium has six fewer dots than the electron dot diagram of neon.
the electron dot diagram of helium has eight fewer dots than the electron dot diagram of neon.
both the electron dot diagram of helium and the electron dot diagram of neon have two dots.
both the electron dot diagram of helium and the electron dot diagram of neon have eight dots.

Explanation:

• Electron dot diagrams (Lewis dot structures) represent the valence electrons of an atom.
• Helium (\(He\)) has an atomic number of \(2\). Its electron configuration is \(1s^{2}\). The first energy level (\(n = 1\)) can hold a maximum of \(2\) electrons. So, helium has \(2\) valence electrons.
• Neon (\(Ne\)) has an atomic number of \(10\). Its electron configuration is \(1s^{2}2s^{2}2p^{6}\). The second energy level (\(n=2\)) can hold a maximum of \(8\) electrons. But when drawing the electron - dot diagram for noble gases, we consider the outermost (valence) electrons. For neon, the valence - shell (\(n = 2\)) has \(8\) electrons.

Answer:

The electron dot diagram of helium has six fewer dots than the electron dot diagram of neon.