BECE Science 2011 Paper

Concept:Noble gases are the unreactive elements belonging to group 18 of the periodic table.Explanation:Group 18 includes helium ($\mathrm{He}$), neon ($\mathrm{Ne}$), argon ($\mathrm{Ar}$), krypton ($\mathrm{Kr}$), xenon ($\mathrm{Xe}$), and radon ($\mathrm{Rn}$).These gases have completely filled valence electron shells, which makes them very stable.Due to this stable electronic configuration, they have extremely low chemical reactivity.As a result, noble gases rarely form molecules and are usually found as monoatomic gases.Among the choices given, chlorine, nitrogen, and oxygen are reactive non-metals, not noble gases.Neon ($\mathrm{Ne}$) is a member of group 18 and is therefore a noble gas.Answer:Neon ($\mathrm{Ne}$), which is option B.