The reactivity of neon and sodium differs significantly due to their positions in the periodic table, which is influenced by their atomic numbers, periods, and groups. Here are the key points explaining this difference:
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Noble Gas vs. Alkali Metal: Neon (atomic number 10) is a noble gas located in Group 18 of the periodic table, while sodium (atomic number 11) is an alkali metal located in Group 1. Noble gases, including neon, are characterized by having full valence electron shells, which make them chemically stable and largely non-reactive. In contrast, alkali metals like sodium have a single electron in their outermost shell, making them highly reactive as they tend to lose that electron easily to achieve a more stable electron configuration.
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Electron Configuration: The electron configuration for neon is \(1s^2 2s^2 2p^6\), indicating a full outer shell with eight electrons (the octet rule). This full outer shell results in low reactivity, as neon does not seek to gain or lose electrons. Sodium's electron configuration is \(1s^2 2s^2 2p^6 3s^1\), showing that it has one electron in its outermost shell, which it can easily lose to form a cation (Na\(^+\)), leading to a higher reactivity.
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Period and Reactivity Trends: In the periodic table, reactivity increases for metals down a group and decreases across periods from left to right. Since sodium is located in Group 1 and has a lower ionization energy compared to elements farther right in the same period (including neon), it is much more reactive. Neon, being in Group 18, exhibits minimal reactivity due to the stability of its filled valence shell.
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Chemical Behavior: Since sodium readily reacts with nonmetals (like chlorine) to form compounds (such as NaCl), it is known for its vigorous reactions. Neon, conversely, does not form stable compounds under normal conditions and remains in a gaseous state as a pure element.
In summary, the fundamental difference in reactivity between neon and sodium can be attributed to neon’s complete valence electron shell, resulting in its non-reactive nature, versus sodium's tendency to lose its outer electron and engage in reactions, highlighting the stark contrast between noble gases and alkali metals in terms of chemical behavior.